Single step preparation of CeO<SUB>2</SUB>/CeAlO<SUB>3</SUB>/&#947;-Al<SUB>2</SUB>O<SUB>3</SUB> by solution combustion method: phase evolution, thermal stability and surface modification

Phase evolution of CeO2/CeAlO3/&#947;-Al2O3 system synthesized from single step solution combustion method is examined here. The nominal compositions of ceria and alumina in (CeO2)x/(Al2O3)1-x are varied from x = 0.0 to 0.66 to yield end compositions, &#947;-Al2O3 to stoichiometric CeAlO3 phase. For the composition x = 0, the phase formed is &#947;-Al2O3, and for x = 0.2, CeAlO3 is formed over &#947;-Al2O3. As the cerium content increased beyond x = 0.2, CeO2/CeAlO3/&#947;-Al2O3 oxides are formed. Heating CeAlO3/&#947;-Al2O3 in air above 700 &#176;C resulted in transformation to CeO2/&#947;-Al2O3 and the subsequent reduction in H2 gave back CeAlO3/&#947;-Al2O3. TEM studies showed CeAlO3 crystallites growth on &#947;-Al2O3 and the oxidized sample showed CeO2 formation over CeAlO3, which in turn interfaced with &#947;-Al2O3 phase. XPS analysis of CeAlO3/&#947;-Al2O3 phase showed the presence of Ce in +3 and +4 state indicating surface oxidized CeAlO3 phase. Epitaxial relation for growth of CeAlO3 over &#947;-Al2O3 and CeO2 over CeAlO3 is demonstrated in the study, where adhesion of CeO2 over &#947;-Al2O3 is via CeAlO3 phase at the interface