Laboratoire Laboratoire d’Electrochimie et de Physicochimie d’Electrochimie et de Physicochimie des Matériaux et des Interfacesdes Matériaux et des Interfaces Glasses : particularities, synthesis and applications

Jean Louis SOUQUET, Michel DUCLOT ELSA

ELECTRICAL PROPERTIES OF GLASSES

INORGANIC GLASSESCONDUCTIVITY NATURE AND APPLICATIONS

Pure ionic conductivity :

Pure electronic conductivity :

- demonstrated one century ago

- mainly due to monovalent cations Li+, Na +, Ag+

- ionic exchange for :glass strengtheningoptical guides

- selective electrodes- solid state batteries- electrical boosting in glass industry (T > Tg)

- by electronic transferbetween localized states

- xerography- photovoltaïc cells- memory effect

Mixed (ionic + electronic) conductivity :

- alkali cations and - electronic transfer

- electrodes materials- electrochromic devices

BE 1

BE 2

BE 3

IONICALLY CONDUCTING GLASSESnetwork formerdoping saltLi+OOOO-OOOO-OLi+Li+OOOOLi+O-I -network modifierA naïve picture of aLi conductive glassTHE COMPONENTS :Doping salts :Network formers :SiO2

P2O5

B2O3

SiS2

GeS2

Network modifiers :Li2O

Ag2O

Li2S

NaCl

Na2S

LiI

AgI

NaCl

Li2SO4

A pure cationic conductivity (tM+ 1)

The macromolecular network is "frozen" solid like behaviour

The best conductivity is obtained with lithium sulfide glasses

σ 10 .S cm-1Li+300 K-3~~

BE 4

WHAT IS A CHARGE CARRIER IN A GLASS ?Ionic pair formation :The charge carriers formation :The charge carriers activated migration : μ+ = F D+ R TSiOMSiSiSiMOO2+MO+_ _+ = ( P expΔHmRT)σ = ( -T A expEσRT)AEσσ = T (expRTΔHf2ΔHm)F2 C l 2 νo6 R exp(ΔSf2R)C+ = C exp ( ΔGf2RT) μ+ =F l 2 νo6 R TP

σ*cσr0dσσMolten saltSURFACE TREATEMENTS BY IONIC EXCHANGE BELOW T gStress enhancement :For an elliptic flaw :(Griffith's law)σd=0*=σ.2.cr0Compression stress by ionic exchange :K+Na+Ionic exchange of K+ for Na+

(rK+ = 1.33 A ; rNa+ = 0.95 A)

produce a compressive layer

(# 100 μm).

The resulting surface stress

decrease the local stress at the

flaw bottom and prevent

crack growth.

oo

BE 5

Exemple : component one to two wave guide by ionic exchangeOPTICAL WAVE GUIDES BY IONIC EXCHANGEBE 6Manufacturing of wave guides :Classical diffusionElectrodesSubstrateMolten salts bathNa+Ag+Na+Ag+-+GField-assisted diffusionn nsubstratenair10-20 mμnsubstratenairλ, Pλ, P/2λ, P/2

ION - SENSITIVE AND pH ELECTRODESA sodium sensitive electrode : E(1)(2)Ag / AgCl(2)(1)(a)(b)reference solution(NaCl)

reference electrodeselectiveelectrodeNa conducting glass membrane

+pH electrode :

A Li+conductive glass with a strong interference with H+

a) without interfering catione = RTFln[Na+]1[Na+]2lnEmeas = RTF[Na+]1 + cte<<UH+ULi+[[Li+] + k (EpH = RTFln) [H+]]over 106 electrodes / year in the worldb) with interfering cation (i.e. K+)[[Na+] + k (E'meas = FRTlnUK+UNa+) [K+]]BE 7

BE 8

THIN FILM LITHIUM BATTERIES WITH GLASSY

ELECTROLYTES AND POSITIVE

After HEF R&D Company (France)Glass electrolyte : 0.38B2O3-0.31Li2O-0.31Li2SO4 (1 μ )m : Amorphous positive TiO0.22S1.4 (2 μ )m

: (5 Negative Li μ )m

Electrical characteristics- output voltage : 2.5 V- average : 2 V- capacity (C) : 50 to 300 μ / 2Ah cm- : 1 / 2short circuit current mA cm- 10 charging until C- no self discharge- : number of cycles several

thousand without damage

BE 9

INDUSTRIAL PROCESS FOR THIN FILM LITHIUM

BATTERIES MANUFACTURING

N°5N°6

BE 10

Currently Cohen and Turnbull (1959)k (T - To) Vf =CHARGE CARRIERS FORMATION AND MIGRATION

OVER Tg FOR A CATIONIC ELECTROLYTE

C+ = C exp (- ΔGf2RT)P = (-expΔHmRT) :with a probabilityF2 C l 2 νo6 R exp(ΔSf2R)σ+ T = exp(-ΔHf2RT)[P + P'(1 - P)]AAt all temperatures, both charge carriers formation and migration processes remain activated mechanisms .But for temperature over T0 (ideal glass transition temperature) ) a new cooperative migration with chain movements appearsP' = exp(-)Vf *Vfcritical free volume for an elementary jumpmean free volume available for T > T0 (ideal glass transition temperature)

(an entropic process)A similar relationship may be derived assuming that the kinetic energy of any particule (charge carrier) in its free volume is proportionnal to the thermal energy received between T and T0 :

PV f=R(T-T0)V f=R(T-T0)Por P' = exp(-R(T - To))PV*fThen

When the two processes P and P' coexist :

BE 11

BE 12

At high temperature (1000 - 1500°C) the ionic conductivity

becomes high enough (10 -2 - 10 -1 S.cm -1) to allow an additionnal

heating by Joule effect.

- Molybdenium electrodes are immersed in “molten” glass.

- Electrical consumption of about 1 kWh for 1 glass ton.

- Among some advantages :

* Increase in furnace production and life time (especially for

roof refractories).

* Decrease the molten glass content and allow a faster

modification of the glass composition.

* Improve the glass quality by a more homogeneous heating.

Raw materialsMo electrodesAirSmokes“Molten glass”

ELECTRICAL “BOOSTING” OF GLASS FURNACES

BE 13

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- SiO2

- TeO2

- P2O5

- Fe2O3

- V2O5

- WO3

While synthesis :

2 V+V + O2- 2 V+IV + 1/2 O2

An electronic transfer between localized states :

V+IV

V+V

V+V

V+V

V+IV

V+IV

OXYDE BASED ELECTRONICALLY

CONDUCTING GLASSES

Network former Transition metal oxydes

BE 15

BE 16

D+ and D- migration in an electric field by a bipolaron

hopping process :

ELECTRONIC DEFECT FORMATION IN

AMORPHOUS SELENIUM AND RESULTING

CONDUCTIVITY BETWEEN LOCALIZED STATES

Se : (Ar) 3d10 4s2 4p4(D : dangling bond)Defects formation : 2D0 D+ + D-Photochemical formation of two dangling bond (D0)SeSeSeSeSeSeSehνSeSeSeSeSeSeD+ D- SeSeESeSeSeSeSeSeD+ D- SeSe

BE 17