Stability of Ultrafine Tetragonal ZrO2 Coprecipitated with Al2O3 by the Spray‐ICP Technique

Abstract

The transformation of ultrafine powders (particle size, 0.01 to 0.04 μm) of the system ZrO2–Al2O3, prepared by spraying their corresponding nitrate solutions into an inductively coupled plasma (ICP) of ultrahigh temperature, was investigated. The powders were composed of metastable tetragonal ZrO2 (mt‐ZrO2) and γ‐Al2O3. On heating, the mt‐ZrO2 (or tetragonal ZrO2, t‐ZrO2) was retained up to 1200°C. At 1380°C the transformation to monoclinic ZrO2 (m‐ZrO2) occurred and the amount of the m‐ZrO2 decreased with the increase in Al2O3 content, thus indicating the stabilization of the t‐ZrO2 by the Al2O3, which seems to be explained in terms of the retardation of grain growth.