STRUCTURAL AND SPECTROSCOPIC STUDIES OF RARE EARTHS DOPED CERIA (RE(La,Sc,Yb):CeO2) NANOPOWDERS

The simple and cost-effective citrate-nitrate auto-combustion method was used for the synthesis of rare-earth (RE) ion-doped ceria (RE(La,Sc,Yb):CeO2), Ce0.9La0.1O1.95, Ce0.9Sc0.1O1.95 and Ce0.9Yb0.1O1.95, nanoparticles. The as-synthesised powders were calcined at 700 C and converted into cylindrical compacts by sintering at 1200 C. XRD confirmed that all the combinations crystallised with the same cubic fluorite structure as pure ceria. The microstructure of the synthesised powders and sintered bodies was examined by SEM and TEM and the particles size of rare-earth (RE) doped ceria was in the range 20 to 50 nm. The optical absorption by functional molecules, impurities and oxygen vacancies was analysed by FTIR and Raman spectroscopy. From the FTIR spectrum, the absorption peaks at 1070 and 550 cm-1 were attributed to the vibrations of metal-oxygen bonds. The characteristic Raman peak was observed at 460 cm-1 and the weak absorption of oxygen vacancies was observed in the region 460-600 cm-1. The microhardness values of the sintered compacts, measured using Vickers indentation, showed hardness values in the range 4700 to 7200 MPa.