Effect of Cooling Rate on Dopant Spatial Localization and Phase Transformation in Cu‐Doped Y‐Stabilized ZrO2 Nanopowders

Abstract

The effect of calcination temperature (TC = 500–1000 °C) and cooling rate on the dopant distribution in Cu‐doped Y‐stabilized ZrO2 nanopowders is studied. The powders are produced by co‐precipitation technique and investigated by attenuated total reflection, UV‐vis diffuse reflectance, electron paramagnetic resonance, and transmission electron microscopy methods. The cooling rate is found to affect the amount of Cu substances on grain surface, the powders subjected to fast cooling (quenching) showed higher amount of Cu‐related complexes on the grains’ surface than their counterparts cooled with furnace after calcination. It is observed that Cu impurities diffuse inside ZrO2 grains from Cu‐related surface substances when TC < 800 °C. This process is accompanied by the enhancement of 275‐nm absorption band caused by oxygen vacancies formation. For TC > 800 °C, outward migration of Cu dopants takes place. Simultaneously, the intensity of 275‐nm absorption band decreases, the monoclinic ZrO2 phase forms and its contribution rises with TC. It is proposed that monoclinic phase formation is caused by the replacement of Cu atoms from lattice sites to interstitials leading to an appearance of the channels for Y out‐diffusion via cation vacancies and destabilization of ZrO2 tetragonal phase.