Stabilization of cubic phase in dense Eu2O3 ceramics

Abstract

Eu2O3, a technologically relevant lanthanide sesquioxide, crystallographically morphs from cubic to monoclinic symmetry at 1170°C. A combined x-ray diffraction/confocal Raman microscopy study is performed on sintered Eu2O3 pellets. After sintering at 1500°C, cubic grains are experimentally observed to form at specific locations, mainly monoclinic grain boundaries, of the surface of Eu2O3 dense ceramics. They cover roughly 10% of the surface and present low crystallinity. The large internal stresses that arise during densification are proposed to be the cause for the observed phenomenology. This surprising phase coexistence advances the appealing prospect of room temperature stabilization of the cubic phase in dense lanthanide sesquioxides sintered at high temperatures.