RELATIONS BETWEEN SUBLATTICE DISORDER, PHASE-TRANSITIONS AND CONDUCTIVITY IN NASICON

Raman and IR spectra were recorded on NASICON type compounds in the 77K-900K temperature range. The NASICON structure domain of stability has been investigated in the M//2O-M prime O//2-SiO//2-P//2O//5 system (M equals Li,Na,K,Ag - M prime equals Hf,Zr,Sc,Ti). Metastability phenomena have been pointed out. The different compounds have been synthesized in the form of powder using a sol-gel process and in the form of single crystals. Conductivity and DTA measurements were performed. The influence of the 'thermal history' and of impurities or dopants on the local order is pointed out.