Relationship between morphology and structure of shape‐controlled CeO₂ nanocrystals synthesized by microwave‐assisted hydrothermal method

Abstract

The influence of synthesis conditions on morphology and structure of CeO 2 nanocrystals prepared by microwave‐assisted hydrothermal method were studied by XRD, TEM, Raman spectroscopy and photoluminescence measurements. Decisive effect of the OH ‐ /Ce 3+ molar ratio in the reaction mixture on the size and shape of CeO 2 nanocrystals was established and explained. Rise of the concentration of OH ‐ groups at the surface of growing CeO 2 nanocrystals promotes shape transformation from irregular (spheroidal) to cube and enables oriented attachment mode of particle growth. I was found that the unit cell parameter and intensity of Ce 3+ defect related band in the luminescence and Raman spectra in ceria nanoparticles increase as follows: irregular shape nanocrystals < large cube < small primary cube shape particles. The reason is growing contribution of total subsurface volume under {100} faces, exposed by ceria nanocubes, where enhanced concentration of Ce 3+ and oxygen vacancies occur.