Effect of ZrO<sub>2</sub> Addition on the Sintering Characteristic and Microstructure of β″-Al<sub>2</sub>O<sub>3</sub>

Abstract

The Na-β″-Al2O3 electrolyte possessing high sodium ion conductivity is a candidate material for secondary batteries and thereto-electric converters. Sintered compacts of β″-Al2O3 containing 0-10vol% of ZrO2 were made from calcined powder consisting of β″-Al2O3 and β-Al2O3. The effects of the ZrO2 addition on the normalized index f(β″) and microstructure of the sintered compacts were investigate, and the improvement of the density and normalized index was observed. It is therefore suggested that the ZrO2 addition to β″-Al2O3 accelerates diffusion of the materials. The small amount of ZrO2 is dissolved into the liquid which is generated during heat treatment. The dissolution ability or surface tension of that liquid appears to be influenced by the dissolution of ZrO2, leading to improved sintering characteristics. The addition of ZrO2 affects the microstructure, especially the grain growth of Al2O3. While abnormal grain growth of Al2O3 takes place in the case of 0.1vol% of ZrO2 addition, such abnormal grain growth is prevented by a 1vol% of ZrO2 addition. The concentration of Zr at the grain boundary, which decreases grain boundary mobility, was observed. The concentration of Zr is therefore considered to prevent abnormal grain growth.