Lithium ion conductivity and thermal behaviour of glasses and crystallised glasses in the system Li2O–Al2O3–TiO2–P2O5

The effects of Al2O3 doping on ionic conductivity and glass stability against crystallisation in the glass system Li2O–TiO2–P2O5 have been investigated using differential scanning calorimetry and ac impedance spectroscopy. Glass samples of the general molar composition (50+x)Li2O:xAl2O3:(10−2x)TiO2:40P2O5 (0≤x≤4.5) were prepared by air quenching of melts. The highest conductivity at 350°C (σ350=2.00×10−2 S cm−1) and lowest activation energy, Ea=0.50 eV, were exhibited by glasses at the x=0.5 composition. This composition also shows the greatest stability against crystallisation (Tc−Tg=146°C). The electrical behaviour of the cast, powdered and crystallised glasses was examined. At x=0.5 the conductivity of the crystallised cast glass at room temperature exceeded that of the parent glass. The structural role of Al in the glasses is discussed with respect to variation in the network modifier to network former ratio on substitution for Ti.