Crystal growth of tetragonal ZrO2 in the glass system ZrO2-SiO2 prepared by the sol-gel process from metal alkoxides

Abstract

Glasses in the system ZrO2-SiO2 containing 40 to 60 mol % ZrO2 were prepared by the sol-gel process from metal alkoxides. Tetragonal ZrO2 was precipitated by heat treatment at 800 and 1200° C, and its crystal growth was measured by differential thermal and X-ray diffraction analyses. At 800 to 900° C, tetragonal ZrO2 crystals grew three-dimensionally and the activation energy for growth was calculated as about 680 kJ mol−1. On the other hand, the secondary growth of tetragonal ZrO2 at 1000 to 1200° C followed the cube-root-of-time law. The activation energy for secondary growth was about 380 kJ mol−1. It is suggested that the diffusion of Zr4+ ions is the rate-limiting process for the secondary crystal growth of tetragonal ZrO2.