Glass-ceramics specimens which were composed of the crystalline phase, LiM2(PO4)3 (where M was Ti or Ge and the M4+ ions were partially replaced by Al3+ ions), were prepared by the heat-treatment of Al2O3-MO2-P2O5 glasses. As-prepared and annealed glasses and glass-ceramics were characterized by using X-ray diffraction, differential scanning calorimetry, XPS and conductivity techniques. The glass transition temperatures of the annealed glasses were found to be 601 and 474C for the Ti and Ge glass systems, while the crystallization temperatures of the annealed glasses were 644 and 578C, respectively. The XPS studies showed that the O 1s spectra for all the glasses and glass-ceramics could be deconvoluted into 2 peaks which corresponded to non-bridging and bridging O atoms. In the case of the Al2O3-Li2O-GeO2-P2O5 system, the deconvoluted Ti XPS spectra indicated the existence of 2 oxidation states of Ti: 3+ and 4+. The Ti 2p and Ge 3p core levels were typified by high binding energies; thus suggesting that Ti4+-O and Ge4+-O bonds were highly ionic in nature. The glass-ceramics exhibited fast ion conduction: 6.53 x 10-4S/cm (Ti system) and 3.99 x 10-4S/cm (Ge system) at 303K. The activation energy was equal to 0.31eV. These conductivity values were slightly higher than those of the corresponding crystalline Li1+xM2-xAlxP3O12 phases, and were 4 to 5 orders of magnitude higher than those of the corresponding glassy phases.

XPS and Ionic Conductivity Studies of Li2O-A12O3-GeO2-P2O5 or (GeO2)-P2O5 Glass-Ceramics. B.V.R.Chowdari, G.V.S.Rao, G.Y.H.Lee: Solid State Ionics, 2000, 136-137, 1067-75