Eutectoid decompositions in Ce-containing ABO₃ perovskites: Part II, the case of divorced growth in CeCrO₃

A eutectoid phase transformation was exhibited by the perovskite CeCrO₃ when heated in air. The kinetics of the reaction, microstructure of the product, and mechanisms of the transformation were studied using thermogravimetric analysis, X-ray and Raman spectroscopy, X-ray diffraction, and electron microscopy. Fluorite CeO₂ and corundum Cr₂O₃ were formed from the decomposition of CeCrO₃. The CeO₂ particles were porous and polycrystalline, a consequence of nucleation, growth, and impingent of CeO₂ domains on the CeCrO₃ particles. Anisotropic growth is indicated by the morphology of the CeO₂ grains, while the Cr₂O₃ particles were single crystals without any crystallographic orientation relationship to the parent phase. Unlike the CeAlO₃ eutectoid, the microstructure comprised of CeO₂ and Cr₂O₃ show no characteristics of a microstructure formed by cooperative growth. The disparity between the eutectoid reactions in CeCrO₃ and CeAlO₃ is attributed to a difference in interfacial energy between the fluorite and sesquioxide phases (i.e., CeO₂/Al₂O₃ versus CeO₂/Cr₂O₃).