Glass samples, Li0.99PO2.55N0.30, with various Li contents were prepared by melting them at high temperatures in flowing NH3 for 16 to 72h, and their structures were investigated by using X-ray photo-electron spectroscopy and liquid chromatography. Two types of P-N bond formed in the glasses. These were the doubly-coordinated (P-N=P) and triply-coordinated (P-N<PP) forms of N. The chromatographic data indicated that N incorporation changed the distribution of phosphate anion chains, and formed -N= linked phosphate anion chains. Alternating-current impedance measurements showed that the incorporation of N into the glass structure increased the ionic conductivity. The highest conductivity was found for the above composition, for which the conductivity was equal to 3.0 x 10-7S/cm at 25C and the activation energy was equal to 0.60eV. The increase in ionic conductivity of the nitrided samples was explained in terms of an increasing structural cross-linking that was similar to the so-called mixed-anion effect, and in terms of a decreased electrostatic energy which occurred when the P-O bond was replaced by the more covalent P-N bond.

B.Wang, B.S.Kwak, B.C.Sales, J.B.Bates: Journal of Non-Crystalline Solids, 1995, 183[3], 297-306