Structural and spectroscopic studies of rare earths doped ceria (RELa,Sc,Yb:CeO2) nanopowders

In the present article, a simple and cost-effective citrate nitrate auto-combustion method was used for the high-yield synthesis of rare-earth (RE) ions doped ceria (RELa,Sc,Yb:CeO2) in the form of Ce0.9La0.1O1.95, Ce0.9Sc0.1O1.95 and Ce0.9Yb0.1O1.95 nanoparticles. The as-synthesized powders were calcined at 700 °C and converted into cylindrical compacts by sintering at 1200 °C. The X-ray diffraction study confirmed that all the combinations crystallized as the cubic fluorite structure of pure ceria. The microstructure of the synthesized powders and sintered bodies was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The particles size of the rare-earth (RE) doped ceria was found to be in the range from 20 to 50 nm. The optical absorption by functional molecules, impurities and oxygen vacancies was analyzed by FTIR and Raman spectroscopic studies. From the FTIR spectrum, the absorption peak found at 1070 and 550 cm−1 was attributed to the vibrations of metal–oxygen bonds. The characteristic Raman peak was observed at 460 cm−1 and weak absorptions of oxygen vacancies were observed in the region 460–600 cm−1. The micro-hardness values of the sintered compacts were measured using Vickers indentation experiments. The hardness values of the RELa,Sc,Yb:CeO2 were in the range from 4700 to 7200 MPa.