Electrical conductivity of Ag+/Na+ ion-exchanged titanosilicate glasses

Abstract The Ag 2 O–TiO 2 –SiO 2 glasses were prepared by Ag + /Na + ion-exchange method from Na 2 O–TiO 2 –SiO 2 glasses at 380–450 °C below their glass transition temperatures ( T g ), and their electrical conductivities were investigated as functions of TiO 2 content and the ion-exchange ratio (Ag/(Ag+Na)). In a series of glasses 20R 2 O· x TiO 2 ·(80− x )SiO 2 with x =10, 20, 30 and 40 in mol%, the electrical conductivities at 200 °C of the fully ion-exchanged glasses of R=Ag were in the order of 10 −5 or 10 −4 S cm −1 and were 1 or 2 orders of magnitude higher than those of the initial glasses of R=Na. The glass of x =30 exhibited the highest increase of conductivity from 3.8×10 −7 to 1.3×10 −4 S cm −1 at 200 °C by Ag + /Na + ion exchange among them. When the ion-exchange ratio was changed in 20R 2 O·30TiO 2 ·50SiO 2 system, the electrical conductivity at 200 °C exhibited a minimum value of 7.6×10 −8 S cm −1 around Ag/(Ag+Na)=0.3 and increased steeply in the region of Ag/(Ag+Na)=0.5–1.0. When the ion-exchange temperature was changed from 450 to 400 °C, the conductivity of the ion-exchanged glass of x =30 decreased. The infrared spectroscopy measurement revealed that the ion-exchange temperature of 450 °C induced a structural change in the glass of x =30. The T g of the fully ion-exchanged glass of x =30 was 498 °C. It was suggested that the incorporated silver ions changed the average coordination number of titanium ions to form higher ion-conducting pathway and resulted in high conductivity in the titanosilicate glasses.