Characterization of Na₂Zn₂TeO₆ ceramic solid electrolyte densified by hot pressing

Abstract

In this work, we applied hot pressing (HP) for the densification of Na2Zn2TeO6 (NZTO) at lower temperature than conventional furnace sintering (FS). Calcined NZTO powder was densified by HP at 700°C for 1 hour under uniaxial pressure of 20 and 60 MPa using a graphite mold. By increasing the uni‐axial pressure to 60 MPa for HP, high relative density above 90 % was obtained. As‐prepared NZTO by HP showed total (bulk + grain‐boundary) ionic conductivity of 0.29 mS cm−1 at room temperature, which is lower than NZTO prepared by FS at 800°C ( = 0.4 mS cm−1) with lower relative density (< 85 %). It was found that the contribution of grain‐boundary resistance in as‐prepared NZTO by HP is larger than NZTO by FS. We confirmed that the grain‐boundary resistance was significantly reduced by post‐annealing. Consequently, total conductivity at room temperature was improved to 0.42 mS cm−1 and 0.56 mS cm−1 by annealed at 700°C and 800°C for 2 hours. X‐ray photoelectron spectroscopy analysis indicated the residual carbon‐contained secondary phases were reduced by post‐annealing. These secondary phases could be formed by the carbon contamination from a graphite mold for HP and their removal by post‐annealing results into the improvement ionic conduction at grain‐boundary.This article is protected by copyright. All rights reserved