M.D. Mezcua , J. Ricote, D.Chateigner , C. Gutiérrez...

SOLUTION DERIVED LEADSOLUTION DERIVED LEAD-- FREE (BiFREE (Bi0.50.5NaNa0.50.5)TiO)TiO33––BaTiOBaTiO33 (BNBT) (BNBT)

THIN FILMS IN THE PROXIMITY OF THE MORPHOTROPIC PHASE THIN FILMS IN THE PROXIMITY OF THE MORPHOTROPIC PHASE

BOUNDARY (MPB)BOUNDARY (MPB)

M.D. Mezcua, J. Ricote, D.Chateigner1, C. Gutiérrez-Lázaro, I. Bretos, R. Jiménez, R. Sirera2 and

M.L. Calzada

Instituto de Ciencia Instituto de Ciencia

de Materiales de Madridde Materiales de Madrid

M.L. CalzadaInstituto Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas (ICMM-CSIC). Cantoblanco. 28049

– Madrid. Spain. 1 Laboratoire de Cristallographie et Sciences des Matériaux (CRISMAT). Ecole Nationale Supérieure d'Ingénieurs de Caen

(ENSICAEN). Université de Caen. 14050 – Caen. France.2 Departamento de Química y Edafología. Facultad de Ciencias. Universidad de Navarra. 31080 – Pamplona, Navarra.

Spain.

1. Index Solution derived lead-free BNBT thin films Solution derived lead-free BNBT thin films



1. Objectives

1. Objectives Solution derived lead-free…Solution derived lead-free…



1. Objectives

• The main goal of this work is the study of

lead-free ferroelectric oxides based on the

(1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 (BNBT) system

to replace the well known Pb(ZrxTi1-x)O3 (PZT)

and the manufacturing of these materials as

thin films for its integration in microelectronic

Solution derived lead-free BNBT thin films Solution derived lead-free BNBT thin films



thin films for its integration in microelectronic

devices.

Lead-free compositions to substitute lead based- on compositions (PZT)

1. Objectives Solution derived lead-free BNBT thin films Solution derived lead-free BNBT thin films



Preparation of thin

films

Integration of ferroelectric

materials in the

information technologies

(ITRS 2011)

Actual trends on the

manufacturing of thin films

2. Introduction

2.Introduction Solution derived lead-free BNBT thin films Solution derived lead-free BNBT thin films



2. Introducción

MPB

Solution derived lead-free…Solution derived lead-free…

BNT-BT

Phase diagram

(1-x)(Bi0.5Na0.5)TiO3-xBaTiO3 (BNBT) Solid solution

Morphotropic phase

boundary(MPB)



Thomas et al. Solid State Sci 2008; 10:934-940

MPB

Takenaka et al. Jpn J Appl Phys 1991; 30: 2236-39

2. Introduction

Bulkceramics

Thin platesThickfilms

Thin filmsUltra- thinfilms

Nano-sozedsystems

1950

100 µm 10 µm 1 µm 100 nm 1 nm1 mm

1970 1990 >2000

Towards the miniaturization of ferroelectric materials and

their integration into microelectronic devices

High permitivity

DRAMs

Electro-optic activity




Piezoelectricity

Pyroelectricity Ferroelectricity

NVFRAMs

Infrared sensor Sensors Actuators

Ferroelectricfilms

Bretos. Ph. D Thesis UAM 2006

2. Introduction

773-813 K528-673K

Rhombohedralphase

Tetragonal phase

Cubic phase

Bulk ceramic

Bi0.5Na0.5TiO3

Increasing temperature

RhombohedralRhombohedralTetragonalTetragonal

Thomas et al.Solid State Science 2010; 12: 311-17




Bi0.5Na0.5TiO3

0.89Bi0.5Na0.5TiO3-0.11BaTiO3

Single-crystal

X-ray

diffraction

Rhombohedral phasewith tetragonal

inclusions

Tetragonal

TetragonalTetragonal

0.90Bi0.5Na0.5TiO3-0.10BaTiO3

Thin film

Jones et al. Acta Crystallogr B 2000; B56:426-30Jones et al. Acta Crystallogr B 2002; B58:168-78

Cheng et al. Appl Phys Lett 2004; 85: 2319-21

Bretos et al. Mater Lett 2011; 65:2714-2716

Thomas et al.Solid State Science 2010; 12: 311-17

Displacement of the MPB composition

Structural effectsThe reason

could be

3. Experimental Procedure

3. Experimental procedure Solution derived lead-free…Solution derived lead-free…



CH3COOH + OH(CH2)3OH + H2O

MetallicMetallic precursorprecursorSolventsSolvents

Molar ratios

1.0:10.0 f Ti (IV) to

any solvents

10.0 mol% of Bi(III) excess +

10.0 mol% of Na(I) excess

Reflux in air for 8h

Na(OCOCH3).3H2O + Bi(OCOCH3)3 +

Ti(CH3COCHCOCH3)2(OC3H7)2

Bi0.5Na0.5TiO3

Precursor sol

CH3CH2COOH + (CH3CH2CO)2OBaCO3

C4H9OH + CH 3COCH2COCH3

Reflux in air for 2 hStirring at room

temperature

Stirring at room

temperature

C4H9OH

MetallicMetallic precursorprecursor MetallicMetallic precursorprecursorSolventsSolvents SolventsSolvents

SolventsSolvents

BaTiO3

Precursor solution

Ti(OC4H10)

3. Experimental procedure Solution derived lead-free BNBT thin films Solution derived lead-free BNBT thin films



Precursor sol(≈0.60 mol L-1)

Precursor solution(≈ 0.30 mol L-1)

Bi0.5Na0.5TiO3-BaTiO3


C2H5OH

SolventSolvent

Bi0.5Na0.5TiO3-BaTiO3


Hoffmann el al. J Eur Ceram Soci 1999: 19 ;1339-1343Alonso et al. J Am Ceram Soci 2008; 92 [10]: 2218-25

Bi0.5Na0.5TiO3

Precursor sol(10%mol.exc. Bi2O3+10% mol. exc. NaO)

Bi0.5Na0.5TiO3

Precursor sol(BNTs)

BaTiO3

Precursor solution(BT)

Stirring at room

temperature(72 h)

Composition in the vicinity of the MPB

3. Experimental procedure

BNBTs10.0

BNBTs5.5BNBTs6.5BNBTs8.0

BNBTs10.0

BNBT5.5BNBT10.0BNBT15.0


Stoichiometric 10% mol. Bi(III) and Na(I) excesses



Crystallinepowders

Diluted solution toprepare the films by

CSD

Dried ethanolAnnealed at900ºC(1h)

Heat shock

Slowcooling

Crystallization: RTP Schwartz Cr Chim 2004; 7 :433-461

25ºC/ 60s

Vacuum

25ºC/ 120s

Oxygen

22s

650ºC/60s

22s100ºC

Refrigeration

Stoichiometric 10% mol. Bi(III) and Na(I) excesses

4. Results and discussion

4. Results and discussion Solution derived lead-free BNBT thin films Solution derived lead-free BNBT thin films



4.1 Crystalline powders




Structural analysis by XRDof the powders

Nominal composition

StoichiometricExcesses of

NaO and Bi2O3

For different molar




For different molar

ratios of BNT/BTNear to

Coexistence of these structures

Tetragonal Rhombohedral

Morphotropic

phase boundary(MPB)

Takenaka et al. Jpn J Appl Phys 1991; 30: 2236-39

(111)T

(001)T

(100)T

(101)T

(110)T

(002)T

(200)T

(112)T

(211)T

39.3 39.6 39.9 40.2 40.5

(111)T

Inte

nsity (

a.u

.)

2θ(º)

(003

)R

(02

1)Ra)

46.0 46.5 47.0

In

ten

sity (

a.u

.)

2θ(º)

(002)T

(200)T

(202)R

b)


Structural analysis of the crystalline phase in the stoichiometric powders with

different BNT/BT molar ratios

Step used 0.005º/5s Step used 0.005º/5s




20 30 40 50 60

*

* *

* *

*

*

*

(202)R

(111)T

(110)R

BNBTs10.0

BNBTs8.0

BNBTs6.5

Inte

nsity (

a.u

.)

2θ(º)

BNBTs5.5

(101)R

(001)T

(100)T

(012)R

(021)R

(003)R

(002)T

(200)T

(102)T

(201)T

(210)T

(113)R

(211)R

(112)T

(211)T

(104)R

(122)R

*

*

Step used 0.05º/3s

Step used 0.005º/5s Step used 0.005º/5s

Jones et al. Acta Crystallogr B 2000; B56:426-30


JCPDS:36-0640(Rhombohedral

Bi0.5Na0.5TiO3)05-0626(Tetragonal

BaTiO3)

(00

3)R

(02

1)R

(11

1)T

BNBTs6.5Inte

nsity (

a.u

.) BNBTs8.0

a)

46.0 46.5 47.0

Inte

nsity (

a.u

.)

2θ (º)

BNBTs6.5

BNBTs8.0

(200)T

(202)R

(002)T

b)


Structural analysis of crystalline stoichiometric powders fordifferent BNT/BT molar ratios

Deconvolution has been made using program V1-40 and the peaks have been fitted to seudo-voigt 2 function




SAMPLESMOLAR RATIOS

BNT/ BT

NOMINAL COMPOSITION

(stoichiometric)

CRYSTALLINE STRUCTURES

OBTAINED FROM XRD

PATTERNS

BNBTs5.5 94.5/5.5 (Bi0.5Na0.5)0.945Ba0.055TiO3 Rhombohedral

BNBTs6.5 93.5/6.5 (Bi0.5Na0.5)0.935Ba0.065TiO3

Rhombohedral + tetragonal

(MPB)

BNBTs8.0 92.0/8.0 (Bi0.5Na0.5)0.920Ba0.080TiO3

Rombohedral + tetragonal

(MPB)

BNBTs10.0 90.0/10.0 (Bi0.5Na0.5)0.900Ba0.100TiO3 Tetragonal

39.5 40.0 40.52θ (º)46.0 46.5 47.02θ (º)

(001)T

(100)T

(101

)T

(110)T

(111

)T

(00

2)T

(200)T

(112)T

(211)T

39.2 39.6 40.1 40.5 41.0

(111)T

2θ(º)

Inte

nsity (

a.u

.)

(003)R

(021)R

a)

45.2 45.6 46.0 46.4 46.8 47.2

(20

2)R

Inte

nsity (

a.u

.)

2θ

(00

2)T (2

00)T

b)


Structural analysis of the crystalline powders containing excesses of Na(I) and Bi(III)

Step used 0.005º/5sStep used 0.005º/5s




20 30 40 50 60

(211)R

(113)R

BNBT15.0

BNBT10.0

2θ(º)

Inte

nsity (

a.u

.)

BNBT5.5

(101

)R

(001)T

(100)T

(012)R

(11

0)R

(111

)T(0

03)R

(021

)R

(00

2)T

(200)T

(202)R

(102

)T(2

01

)T

(210)T (1

12)T

(211)T

(104

)R

(122)R

*

Step used 0.05º/3s

Step used 0.005º/5sStep used 0.005º/5s



JCPDS:36-0640(Rhombohedral

Bi0.5Na0.5TiO3)05-0626(Tetragonal

BaTiO3)


Structural analysis of crystalline powders with excesses of Na(I) and Bi(III) for different BNT/BT molar ratios

39.2 39.6 39.9 40.3 40.6 41.0

(02

1)R

(00

3)R

(111

)T

Inte

nsity (

a.u

.)

BNBT10.0

a)

45.2 45.6 46.0 46.4 46.8 47.2

(20

2)R

(20

0)T

(00

2)T

BNBT10.0

Inte

nsity (

a.u

.)

b)

Deconvolution has been made using program V1-40 and the peaks have been fitted to seudo-voigt 2 function




SAMPLEMOLAR RATIOS

BNBT/BT

NOMINAL COMPOSITION

(10%molar exceso Bi2O3+

10%molar exceso NaO)

CRYSTALLINE STRUCTURE

OBTAINED FROM XRD

PATTERNS

BNBT5.5 94.5/5.5 (Bi0.5Na0.5)0.945Ba0.055TiO3 Rhombohedral

BNBT10.0 90.0/10.0 (Bi0.5Na0.5)0.900Ba0.100TiO3

Rhombohedral+ tetragonal

(MPB)

BNBT15.0 85.0/15.0 (Bi0.5Na0.5)0.850Ba0.150TiO3 Tetragonal

39.2 39.6 39.9 40.3 40.6 41.02θ(º)

45.2 45.6 46.0 46.4 46.8 47.2

2θ(º)

200

250

300

350

400

Te

mp

era

ture

(ºC

)


Determination of the morphotropic phase boundary(MPB) for the crystalline powders

Stoichiometric nominal compositionNominal composition

containing excesses of Na(I) +Bi(III)

200

250

300

350

400

Te

mp

era

ture

(ºC

)

Cubic

Tetragonal

Cubic

Tetragonal




0 5 10 15 20 25 300

50

100

150

200

Te

mp

era

ture

(ºC

)

(Bi0.5

Na0.5

)1-x

BaxTiO

3 (mol%)

Rout et al. J Ceram Soc Jpn 2009; 117 [7]: 797-800

0 5 10 15 20 25 300

50

100

150

200

Te

mp

era

ture

(ºC

)

(Bi0.5

Na0.5

)1-x

BaxTiO

3 (mol%)

Tetragonal

Rhomboedral

MPB

Tetragonal

Rhombohedral

MPB

4.2 Thin films




Ferroelectric system in thin film form:

•Lost by volatilization of Na(I)+Bi(III)

•Change of the phase because of

structural effects induced by the

substrate

(11

1)

Pt

(20

0)

Pt

(20

0)

Pe

rovskite

Pe

rovskite

Pe

rovskite Pt(

11

1)

Pt

(11

1)

Pe

rovskite

Inte

nsity (

a.u

.)32.0 32.3 32.5 32.8 33.0

Pe

rovskite

R

Pe

rovskite

T

Inte

nsity (

a.u

.)

2θ (º)


XRD patterns of BNBTs thin films without

excesses of any metallic precursor

Step used 0.005º/5s

Reflections from the

substrate




Kβ P

t (1

11)

20 25 30 35 40 45 50

Pt

(20

0)

Pe

rovskite

Pe

rovskite

Bi xP

t (1

11

)

Pe

rovskite

Inte

nsity (

a.u

.)

BNBTs5.5

BNBTs6.5

BNBTs8.0

BNBTs10.0

2θ(º)

Step used 0.05º/3s

Ba2+ has been

incorporated into

the structure


Pt

(20

0)

Pe

rovskite

Pe

rovskite

Pe

rovskite

Pt(

11

1)

Pe

rovskite

Inte

nsity(a

.u.)

Pt

(111)

Pt(

111)

32.0 32.3 32.5 32.8 33.0

In

ten

sity (

a.u

.)

2θ(º)

Pero

vskite T

Pero

vskite R

XRD patterns of BNBT thin films with

addition of Na(I) and Bi(III) excesses in the

nominal composition

Step used 0.005º/5s

Reflections from the

substrate




20 25 30 35 40 45 50

Pe

rovskite

BNBT15.0

BNBT10.0

Inte

nsity(a

.u.)

2θ(º)

BNBT5.5K

βP

t (1

11)

Bi xP

t(1

11)

Step used 0.05º/3s

Ba2+ has been

incorporated into

the structure


-600 -400 -200 0 200 400 600

0

20

40

60

P(µC/cm2)

E (kV/cm)

BNBTs5.5

BNBTs6.5

BNBTs8.0BNBTs10.0

Electrical measurement of BNBTs

nominal stoichiometric thin films

Cross-section and plan-view images of

BNBTs nominal stoichiometric films

2µm

2µm2µm

2µm

BNBTs5.5

BNBTs6.5




-60

-40

-20E (kV/cm)

2µm

2µm 2µm

2µm

2µm

Sample BNBTs5.5 BNBTs6.5 BNBTs8.0 BNBTs10.0

Grain size ≈288 nm ≈194 nm ≈179 nm ≈119 nm

Thickness ≈341 nm ≈459 nm ≈329 nm ≈435 nm

BNBTs6.5

BNBTs8.0

BNBTs10.0

-400 -200 0 200 400

0

30

60

BNBT15.0

BNBT10.0

BNBT5.5

P(µC/cm2)


Electrical measurement of BNBT thin films with

Na(I)+Bi(III) excesses in the nominal composition

Cross-section and plan-view images of

BNBT films containing excesses of

Na(I)+Bi(III) in the nominal composition

2µm2µm BNBT5.5




-400 -200 0 200 400

-60

-30

E (kV/cm)

Sample BNBT5.5 BNBT10.0 BNBT15.0

Grain size ≈153 nm ≈170 nm ≈97 nm

Thickness ≈559 nm ≈553 nm ≈550 nm

2µm

2µm2µm

2µmBNBT10.0

BNBT15.0


20

40

60

P(µC/cm2)

BNBT10.0

BNBTs5.5

Electrical measurements comparison between the best

stoichiometric and the best not stoichiometric films




-600 -400 -200 0 200 400 600

-80

-60

-40

-20

0

E(kV/cm)

5. Conclusions

5. Conclusions Solution derived lead-free BNBT thin films Solution derived lead-free BNBT thin films



5. Conclusions

•The morphotropic phase boundary (MPB) of BNBT powders has

been situated for 93.5/6.5 and 92.0/8.0 ‘stoichiometric’ nominal

composition. Addition of Na(I) and Bi(III) excesses to the system leadsto a shift of the MPB for these powders to the 90.0/10.0 nominal

composition.

•The best ferroelectric response for BNBT films has been obtainedfor the 90.0/10.0 composition with addition of Na(I) and Bi(III)




for the 90.0/10.0 composition with addition of Na(I) and Bi(III)

excesses to the respective precursor solution (Pr 23 µC/cm2 andPs≈60 µC/cm2), the composition for which has identified the MPB in

the crystalline powders.

•Studies are in progress to elucidate the either intrinsic (e.g.

compositional effects) or extrinsic (e.g. scaling effects) driving nature

of the boundary displacement observed in these BNBT films withrespect to bulk counterparts.

SOLUTION DERIVED LEADSOLUTION DERIVED LEAD-- FREE (BiFREE (Bi0.50.5NaNa0.50.5)TiO)TiO33––BaTiOBaTiO33 (BNBT) (BNBT)

THIN FILMS IN THE PROXIMITY OF THE MORPHOTROPIC PHASE THIN FILMS IN THE PROXIMITY OF THE MORPHOTROPIC PHASE

BOUNDARY (MPB)BOUNDARY (MPB)

M.D. Mezcua, J. Ricote, D.Chateigner1, C. Gutiérrez-Lázaro, I. Bretos, R. Jiménez, R. Sirera2 and

M.L. Calzada



M.L. CalzadaInstituto Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Científicas (ICMM-CSIC). Cantoblanco. 28049

– Madrid. Spain. 1 Laboratoire de Cristallographie et Sciences des Matériaux (CRISMAT). Ecole Nationale Supérieure d'Ingénieurs de Caen

(ENSICAEN). Université de Caen. 14050 – Caen. France.2 Departamento de Química y Edafología. Facultad de Ciencias. Universidad de Navarra. 31080 – Pamplona, Navarra.

Spain.

M.D. Mezcua , J. Ricote, D.Chateigner , C. Gutiérrez...

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