Electron paramagnetic resonance (EPR) study of solid solutions of MoO 3 in SbVO 5
17
Electron paramagnetic resonance (EPR) study of solid solutions of MoO 3 in SbVO 5 Janusz Typek Institute of Physics West Pomeranian University of Technology Szczecin, Poland
description
Electron paramagnetic resonance (EPR) study of solid solutions of MoO 3 in SbVO 5. Janusz Typek Institute of Physics West Pomeranian University of Technology Szczecin, Poland. Outline. The aim of th is work Preparation and characterisation of samples - PowerPoint PPT Presentation
Transcript of Electron paramagnetic resonance (EPR) study of solid solutions of MoO 3 in SbVO 5
Electron paramagnetic resonance (EPR) study of solid solutions of MoO3 in SbVO5
Janusz TypekInstitute of Physics
West Pomeranian University of TechnologySzczecin Poland
Outline
bull The aim of this work
bull Preparation and characterisation of samples
bull Results of the EPR study ndash magnetic defects
bull Conclusions
The aim of the work
Why to study these materials
bull They are used widely as catalysts
What are the oxidation states of ionsbull Only assumed on general grounds
What is the structure of the defect centres bull Not known
Components concentration triangle
0 20 40 60 80 100
0
20
40
60
80
1000
20
40
60
80
100
MoO
3 m
ol
Sb 2
O 4
mol
V2O
5 mol
V2O
5Sb
2O
4
MoO3
SbVO5 MoO3
SbVO5
Preparation of samples
Samples of SbVO5 were produced by
heating in air equimolar mixture of V2O5 with α-Sb2O4 in the following
stages
bull stage I 550ordmCrarr600ordmC (48h)
bull stage II 600ordmCrarr600ordmC (48h)
bull stage III 600ordmCrarr620ordmC (24h)
bull stage IV 620ordmCrarr650ordmC (48h)
bull stage V 650ordmCrarr650ordmC (48h)
Samples of MoO3 solid solutions in SbVO5
were made by homogenization of the reagents in suitable proportions by grinding shaped into pastilles and then heated in the following stages
bull stage I 400ordmC (1h)rarr500ordmC (24h)rarr 500ordmC (24h)
bull stage II 600ordmC (48h)
bull stage III 630ordmC (24h)
bull stage IV 645ordmC (24h)
V2O5+Sb2O4+12 O2rarr2 SbVO5 V2O5+Sb2O4+MoO3
Investigated samples
General formulae of the solid solutionsSb1-6x xV1-6xxMo10xO5
Composition of initial mixtures [mol]
Formulae index
xMoO3 V2O5 Sb2O4
500 4750 4750 00051
750 4625 4625 00077
1000 4500 4500 00104
1250 4375 4375 00132
1500 4250 4250 00159
1750 4125 4125 00188
The matrix SbVO5
Scanning Electron Microscope (SEM) picture
Thickness ~05 μm
Length ~3divide10 μm
The SbVO5 matrix crystal structure
Monoclinica=986 Aring b=493 Aring c=712 Aring
β=10979deg Z=4
From IR study it follows that
SbO6 octahedra VO6 deformed octahedra Separate layers
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
Outline
bull The aim of this work
bull Preparation and characterisation of samples
bull Results of the EPR study ndash magnetic defects
bull Conclusions
The aim of the work
Why to study these materials
bull They are used widely as catalysts
What are the oxidation states of ionsbull Only assumed on general grounds
What is the structure of the defect centres bull Not known
Components concentration triangle
0 20 40 60 80 100
0
20
40
60
80
1000
20
40
60
80
100
MoO
3 m
ol
Sb 2
O 4
mol
V2O
5 mol
V2O
5Sb
2O
4
MoO3
SbVO5 MoO3
SbVO5
Preparation of samples
Samples of SbVO5 were produced by
heating in air equimolar mixture of V2O5 with α-Sb2O4 in the following
stages
bull stage I 550ordmCrarr600ordmC (48h)
bull stage II 600ordmCrarr600ordmC (48h)
bull stage III 600ordmCrarr620ordmC (24h)
bull stage IV 620ordmCrarr650ordmC (48h)
bull stage V 650ordmCrarr650ordmC (48h)
Samples of MoO3 solid solutions in SbVO5
were made by homogenization of the reagents in suitable proportions by grinding shaped into pastilles and then heated in the following stages
bull stage I 400ordmC (1h)rarr500ordmC (24h)rarr 500ordmC (24h)
bull stage II 600ordmC (48h)
bull stage III 630ordmC (24h)
bull stage IV 645ordmC (24h)
V2O5+Sb2O4+12 O2rarr2 SbVO5 V2O5+Sb2O4+MoO3
Investigated samples
General formulae of the solid solutionsSb1-6x xV1-6xxMo10xO5
Composition of initial mixtures [mol]
Formulae index
xMoO3 V2O5 Sb2O4
500 4750 4750 00051
750 4625 4625 00077
1000 4500 4500 00104
1250 4375 4375 00132
1500 4250 4250 00159
1750 4125 4125 00188
The matrix SbVO5
Scanning Electron Microscope (SEM) picture
Thickness ~05 μm
Length ~3divide10 μm
The SbVO5 matrix crystal structure
Monoclinica=986 Aring b=493 Aring c=712 Aring
β=10979deg Z=4
From IR study it follows that
SbO6 octahedra VO6 deformed octahedra Separate layers
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
The aim of the work
Why to study these materials
bull They are used widely as catalysts
What are the oxidation states of ionsbull Only assumed on general grounds
What is the structure of the defect centres bull Not known
Components concentration triangle
0 20 40 60 80 100
0
20
40
60
80
1000
20
40
60
80
100
MoO
3 m
ol
Sb 2
O 4
mol
V2O
5 mol
V2O
5Sb
2O
4
MoO3
SbVO5 MoO3
SbVO5
Preparation of samples
Samples of SbVO5 were produced by
heating in air equimolar mixture of V2O5 with α-Sb2O4 in the following
stages
bull stage I 550ordmCrarr600ordmC (48h)
bull stage II 600ordmCrarr600ordmC (48h)
bull stage III 600ordmCrarr620ordmC (24h)
bull stage IV 620ordmCrarr650ordmC (48h)
bull stage V 650ordmCrarr650ordmC (48h)
Samples of MoO3 solid solutions in SbVO5
were made by homogenization of the reagents in suitable proportions by grinding shaped into pastilles and then heated in the following stages
bull stage I 400ordmC (1h)rarr500ordmC (24h)rarr 500ordmC (24h)
bull stage II 600ordmC (48h)
bull stage III 630ordmC (24h)
bull stage IV 645ordmC (24h)
V2O5+Sb2O4+12 O2rarr2 SbVO5 V2O5+Sb2O4+MoO3
Investigated samples
General formulae of the solid solutionsSb1-6x xV1-6xxMo10xO5
Composition of initial mixtures [mol]
Formulae index
xMoO3 V2O5 Sb2O4
500 4750 4750 00051
750 4625 4625 00077
1000 4500 4500 00104
1250 4375 4375 00132
1500 4250 4250 00159
1750 4125 4125 00188
The matrix SbVO5
Scanning Electron Microscope (SEM) picture
Thickness ~05 μm
Length ~3divide10 μm
The SbVO5 matrix crystal structure
Monoclinica=986 Aring b=493 Aring c=712 Aring
β=10979deg Z=4
From IR study it follows that
SbO6 octahedra VO6 deformed octahedra Separate layers
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
Components concentration triangle
0 20 40 60 80 100
0
20
40
60
80
1000
20
40
60
80
100
MoO
3 m
ol
Sb 2
O 4
mol
V2O
5 mol
V2O
5Sb
2O
4
MoO3
SbVO5 MoO3
SbVO5
Preparation of samples
Samples of SbVO5 were produced by
heating in air equimolar mixture of V2O5 with α-Sb2O4 in the following
stages
bull stage I 550ordmCrarr600ordmC (48h)
bull stage II 600ordmCrarr600ordmC (48h)
bull stage III 600ordmCrarr620ordmC (24h)
bull stage IV 620ordmCrarr650ordmC (48h)
bull stage V 650ordmCrarr650ordmC (48h)
Samples of MoO3 solid solutions in SbVO5
were made by homogenization of the reagents in suitable proportions by grinding shaped into pastilles and then heated in the following stages
bull stage I 400ordmC (1h)rarr500ordmC (24h)rarr 500ordmC (24h)
bull stage II 600ordmC (48h)
bull stage III 630ordmC (24h)
bull stage IV 645ordmC (24h)
V2O5+Sb2O4+12 O2rarr2 SbVO5 V2O5+Sb2O4+MoO3
Investigated samples
General formulae of the solid solutionsSb1-6x xV1-6xxMo10xO5
Composition of initial mixtures [mol]
Formulae index
xMoO3 V2O5 Sb2O4
500 4750 4750 00051
750 4625 4625 00077
1000 4500 4500 00104
1250 4375 4375 00132
1500 4250 4250 00159
1750 4125 4125 00188
The matrix SbVO5
Scanning Electron Microscope (SEM) picture
Thickness ~05 μm
Length ~3divide10 μm
The SbVO5 matrix crystal structure
Monoclinica=986 Aring b=493 Aring c=712 Aring
β=10979deg Z=4
From IR study it follows that
SbO6 octahedra VO6 deformed octahedra Separate layers
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
Preparation of samples
Samples of SbVO5 were produced by
heating in air equimolar mixture of V2O5 with α-Sb2O4 in the following
stages
bull stage I 550ordmCrarr600ordmC (48h)
bull stage II 600ordmCrarr600ordmC (48h)
bull stage III 600ordmCrarr620ordmC (24h)
bull stage IV 620ordmCrarr650ordmC (48h)
bull stage V 650ordmCrarr650ordmC (48h)
Samples of MoO3 solid solutions in SbVO5
were made by homogenization of the reagents in suitable proportions by grinding shaped into pastilles and then heated in the following stages
bull stage I 400ordmC (1h)rarr500ordmC (24h)rarr 500ordmC (24h)
bull stage II 600ordmC (48h)
bull stage III 630ordmC (24h)
bull stage IV 645ordmC (24h)
V2O5+Sb2O4+12 O2rarr2 SbVO5 V2O5+Sb2O4+MoO3
Investigated samples
General formulae of the solid solutionsSb1-6x xV1-6xxMo10xO5
Composition of initial mixtures [mol]
Formulae index
xMoO3 V2O5 Sb2O4
500 4750 4750 00051
750 4625 4625 00077
1000 4500 4500 00104
1250 4375 4375 00132
1500 4250 4250 00159
1750 4125 4125 00188
The matrix SbVO5
Scanning Electron Microscope (SEM) picture
Thickness ~05 μm
Length ~3divide10 μm
The SbVO5 matrix crystal structure
Monoclinica=986 Aring b=493 Aring c=712 Aring
β=10979deg Z=4
From IR study it follows that
SbO6 octahedra VO6 deformed octahedra Separate layers
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
Investigated samples
General formulae of the solid solutionsSb1-6x xV1-6xxMo10xO5
Composition of initial mixtures [mol]
Formulae index
xMoO3 V2O5 Sb2O4
500 4750 4750 00051
750 4625 4625 00077
1000 4500 4500 00104
1250 4375 4375 00132
1500 4250 4250 00159
1750 4125 4125 00188
The matrix SbVO5
Scanning Electron Microscope (SEM) picture
Thickness ~05 μm
Length ~3divide10 μm
The SbVO5 matrix crystal structure
Monoclinica=986 Aring b=493 Aring c=712 Aring
β=10979deg Z=4
From IR study it follows that
SbO6 octahedra VO6 deformed octahedra Separate layers
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
The matrix SbVO5
Scanning Electron Microscope (SEM) picture
Thickness ~05 μm
Length ~3divide10 μm
The SbVO5 matrix crystal structure
Monoclinica=986 Aring b=493 Aring c=712 Aring
β=10979deg Z=4
From IR study it follows that
SbO6 octahedra VO6 deformed octahedra Separate layers
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
The SbVO5 matrix crystal structure
Monoclinica=986 Aring b=493 Aring c=712 Aring
β=10979deg Z=4
From IR study it follows that
SbO6 octahedra VO6 deformed octahedra Separate layers
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
Solid solution SbVO5MoO3
SEM picture of SbVO5MoO3 (15mol)
More deformed smaller sizes
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
SbVO5MoO3 - Charge compensation
V5+O6
V5+O6
Sb5+O6
Sb5+O6
Mo6+
Mo6+
Mo6+ Mo6+
Mo6+ Mo6+
Preferred model of charge compensation based on TG bull V5+ and Sb5+ vacancies bull substitution of Mo6+ at V5+ and Sb5+ sites
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
EPR paramagnetic centers
VanadiumV5+ (3p6) nominal nonmagneticV4+ (3d1) defect magnetic S=12AntimonySb5+ (4d10) nominal nonmagneticSb4+ (5s1) defect magnetic S=12MolybdenumMo6+ (4p6) nominal nonmagneticMo5+ (4d1) defect magnetic S=12
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
250 300 350 400 450-8
-6
-4
-2
0
2
4
6
8
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
118 K146 K187 K229 K293 K37 K43 K50 K60 K72 K
The SbVO5 matrix EPR
100 200 300 400 500 600
-2
-1
0
1
2
3
Ab
sorp
tion
de
riva
tive
[a
rb
un
its]
Magnetic fie ld [mT]
T=365 K
D=1910-4 cm-1
bull Only 002 of all vanadium ions are EPR active (V4+)
bull There are separate V4+ (showing 8 hfs narrow lines) and involved in a V4+ndashOndashV5+ bond with mobile electron hopping (broad line)
bull Separate V4+ in SbVO5 exist as VO2+ ions in octahedral coordination with a tetragonal compressionbull There are also pairs of two interacting VO2+ with a singlet S=0 (ground state) and a triplet S=1 state (excited state)
0 20 40 60 80 1000 0
0 2
0 4
0 6
0 8
1 0
(Int
egra
ted
EP
R in
tens
ity)
-1 [a
rb u
nits
]
T e m p e ra t u re [K ]
TCW=8 K
I(T)=C(T-TCW)
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
0
2
4
6
8
10
12
14
16
150 200 250 300 350 400
EP
R a
bsor
ptio
n [a
u]
Magnetic field [mT]
1
2
3
4
56
2000 3000 4000
-400
-200
0
200
400
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-300
-200
-100
0
100
200
300
400
500
2000 3000 4000
-400
-200
0
200
400
2000 2200 2400 2600 2800 3000 3200 3400 3600 3800 4000 4200 4400
-400
-200
0
200
400
2000 2400 2800 3200 3600 4000 4400
-400
-200
0
200
400
1
2
3
4
EP
R s
ign
al i
nte
nsi
ty [a
u]
Magnetic field [G]
56
EPR solid solution SbVO5MoO3
bull No hfs lines visible ndash all V4+ ions strongly coupled to the magnetic spin systembull The intensity of EPR spectra increases with the Mo6+ contents ndash only cation vacancy compensation model could not be used
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
45
50
55
60
65
70
06 08 10 12 14 16 18 20 22 24 26 28
30
32
34
36
38
EP
R in
teg
rate
d
inte
nsi
ty [a
u]
EP
R li
ne
wid
th [m
T]
Concentration of Mo [mole]
EPR solid solution SbVO5MoO3
05 10 15 20 25 30
15
20
25
30
35
Fra
ctio
n o
f Mo
ion
s ca
usi
ng
va
len
ce r
ed
uct
ion
[]
Concentration of Mo ions [ mole]
bull No linear dependence of V4+ content on amount of Mo6+ ionsbull The EPR linewidth decreases with Mo6+ content (exchange interaction narrowing)bull The fraction of Mo6+ ions involved in V5+rarrV4+ compensation decreases with Mo6+
increase
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
Solid solution possible centres
Possible paramagnetic Mo6+-V4+ centres involving one V4+ ion
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
Solid solution possible centres
Possible paramagnetic centres involving more than one V4+ ion (equatorial view)
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
Conclusions
bull At least one third of Mo6+ ions are involved in charge compensation through changing the oxidation state of cations
bull Compensation mechanism through cation vacancy is more efficient for larger concentrations of Mo6+ ions
bull V4+ ions are strongly coupled to the rest of spin system ndash no distant charge compensation
- Slide 1
- Slide 2
- Slide 3
- Slide 4
- Slide 5
- Slide 6
- Slide 7
- Slide 8
- Slide 9
- Slide 10
- Slide 11
- Slide 12
- Slide 13
- Slide 14
- Slide 15
- Slide 16
- Slide 17
-
