Synthesis of Ce1−xErxO2−y nanoparticles by the hydrothermal method: Effect of microwave radiation on morphology and phase composition

Synthesis of Ce1−xErxO2−y nanoparticles by the hydrothermal and microwave assisted hydrothermal method is described. The effect of the amount of Er content and the synthesis method on the phase composition and morphology of the products was studied by X-ray diffraction, scanning and transmission electron microscopy and Raman spectroscopy. For low doping level (x≤0.2), hydrothermal treatment at 220 °C for 24 h produced nanocubes of the mixed Ce–Er oxide with broad, bimodal size distribution. Further addition of Er hinders the growth of abnormally large nanocubes resulting in uniform almost circular oxide particles (10–30 nm). For high doping (x≥0.5) rod-like particles of Er hydroxide were also observed. Use of microwave radiation enabled the synthesis of the nanocubes of the mixed oxides at significantly shorter time (3 h), but this phase always coexisted with rod-like particles of the mixed (Er,Ce)(OH)3 hydroxide. The mechanism of formation of Ce1−xErxO2−y nanocubes with bimodal size distribution is discussed within the framework of the model of oriented attachment.