Ionic conductivity of lithium alumino-silicate thin films on SiO2 glass and Al2O3 substrates

Crystalline and amorphous lithium alumino-silicate thin films were prepared on SiO2 glass and Al2O3 fine ceramics substrates by a pulsed laser deposition (PLD) method. Temperature and thickness dependence of the ionic conductivity was measured at the temperature range from 500 to 700 K. The amorphous thin film shows about one order higher ionic conductivity than that of polycrystalline β-eucryptite. This result suggests that the amorphous structure is important to obtain high ionic conductible thin film. Furthermore, it was proven that the ionic conductivity of the crystalline (β-eucryptite) thin film depends on the substrate species. In contrast to the crystalline thin films, the ionic conductivity of the amorphous thin films does not show substrate dependence. The substrate dependence of ionic conductivity may originate from the texture of the thin film or the structural modulation at the hetero-interface region or both of them.