Extreme behavior of Li-ion conductivity in the Li2O–Al2O3–P2O5 glass system

•We have obtained 50Li2O–xAl2O3–(50 − x)P2O5 glasses with x up to 10.•Conductivity and density change non-linearly with a maximum at 6.25 mol% of Al2O3.•This behavior is attributed to the dramatic structural changes in the glass.

Aluminophosphate glasses with compositions 50Li2O–xAl2O3–(50 − x)P2O5 have been synthesized and analyzed in the x = 0–10 range. The influence of alumina content on the glass transition temperature (Tg), crystallization temperature, thermal stability, density and ionic conductivity has been investigated. When Al2O3 substitutes for P2O5, Tg increases in all glass compositions. Crystallization stability has been found to be a function of alumina content. Ionic conductivity has been studied by impedance spectroscopy. Ionic conductivity and density exhibit a non-linear and non-additive change with a maximum at 6.25 mol% of Al2O3. IR spectroscopy study has indicated the phosphate network depolymerization. NMR technique revealed dramatic structural changes in the glass at x > 6.25. These changes lead to extreme behavior of molar volume and, as a consequence, to a maximum in ionic conductivity.