Characterization of co-fired sodium-ion conductive Na2Ni2TeO6 and Na2Zn2TeO6 with honeycomb layer structure

We investigated the reactivity of P2-type honeycomb layered oxides Na2Ni2TeO6 (NNTO) and Na2Zn2TeO6 (NZTO) co-fired at the temperature from 500 ºC to 800 ºC. From X-ray diffraction measurements, it was found that the reaction between NNTO and NZTO is unremarkable at the temperature below 700 ºC. However, when annealed at 800 ºC, they formed the solid-solution phase without any secondary phases. The NNTO and NZTO composite pellets co-fired at 800 ºC showed sodium-ion conductivity well above 10−4 S cm−1 at room temperature, indicating that the solid-solution phase of NNTO and NZTO has good ionic conductivity. A maximum room temperature conductivity of 7.4 × 10−4 S cm−1 was confirmed at the mixing ratio NNTO : NZTO = 0.5 : 1.5. These results can be applied to the fabrication of all-solid-state batteries using NNTO as the cathode active material and NZTO as the solid electrolyte via a simple co-sintering process.