Raman spectroscopy and X-ray diffraction study of the phase transformation of ZrO2-Al2O3 and CeO2-Al2O3 nanocomposites

Combined UV Raman spectroscopy using radiation of 325 nm, visible Raman spectroscopy excited by 633 nm laser, X-ray diffraction and nitrogen adsorption-desorption surface area measurements were used in the present work to investigate the mechanism of the phase transformation and sintering of ZrO2-Al2O3 and CeO2-Al2O3 nanocomposites synthesized by a nanoparticle-mediated Pechini sol-gel method. These materials were compared to pure alumina, ZrO2 and CeO2 nanoparticles calcined at different temperatures. The modification of the alumina surface with CeO2 and ZrO2 can significantly delay the phase transformation and sintering. UV Raman spectroscopy is found to be more sensitive at the surface region for the ZrO2-Al2O3 and CeO2-Al2O3 nanocomposites, making possible to study the phase changes of the additional oxide. A synergetic stabilization effect between two oxides such as Al2O3 and ZrO2 or CeO2 was found, where the phase transformation and sintering of both oxides were delayed. The results reveal the role of the second oxides in the nanocomposites in suppressing surface-mediated sintering thus gaining a higher stability of the materials at high temperatures. (C) 2010 Elsevier B. V. All rights reserved.