Sintering temperature dependency on sodium-ion conductivity for Na2Zn2TeO6 solid electrolyte

We investigated the sintering temperature dependency on the properties of Na₂Zn₂TeO₆ (NZTO) solid electrolyte synthesized via a conventional solid-state reaction method. Sintering temperature of calcined NZTO powder, which was obtained by the calcination of precursor at 850℃, was changed in the range from 650 to 850℃. X-ray diffraction analysis showed that P2-type layered NZTO phase was formed in all sintered samples without forming any secondary phases. The relative densities of sintered NZTO samples were approximately 83%−85% for the samples sintered at 700℃ or higher. The all sintered samples showed sodium-ion conductivity above 10⁻⁴ S cm⁻¹ at room temperature and the highest conductivity of 4.0 × 10⁻⁴ S cm⁻¹ in the sample sintered at 750℃. The sintering temperature to obtain the highest room temperature conductivity is 100℃ lower than that used in previous works. Such low sintering temperature compared to other Na-based oxide solid electrolytes could be useful for co-sintering with electrode active materials for fabrication of all-solid-state sodium-ion battery.