Study of inorganic solid lithium ion conductor with mixed degrees of sintering

•Li1 + xAlxZr2-x(PO4)3 with mixed degrees of sintering have been achieved.•Conductivities of samples with mixed degrees of sintering are enhanced.•A triclinic phase transforms to a rhombohedral one upon Al doping.

A series of Li1 + xAlxZr2-x(PO4)3 samples with varied amount of Al doping have been prepared using a solid state reaction method and the optimum doping amount of aluminum is determined as 0.6. All the doped samples showed an increased conductivity, which is attributed to the transformation of the triclinic phase to the rhombohedral phase and the density increasement upon doping of Al. By mixing powders calcined at two different temperatures (700 °C and 1100 °C), samples Li1.6Al0.6Zr1.4(PO4)3 with the optimum doping amount of Al have been made to study the effect of the mixed degrees of sintering. The overall conductivities of samples with mixed degrees of sintering are all improved and peaked at 20–30% of powders calcined at 700 °C. This improvement is thought to relate to the role of powders calcained at 700 °C, which acted as “bridges” to connect all the other well-defined grains together.