Single step preparation of CeO2/CeAlO3/γ-Al2O3 by solution combustion method: Phase evolution, thermal stability and surface modification

Phase evolution of CeO2/γ-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, γ-Al2O3 to stoichiometric CeAlO3 phase. For the composition x = 0, the phase formed is γ-Al2O3, and for x = 0.2, CeAlO3 is formed over γ-Al2O3. As the cerium content increased beyond x = 0.2, CeO2/CeAlO3/γ-Al2O3 oxides are formed. Heating CeAlO3/γ-Al2O3 in air above 700 °C resulted in transformation to CeO2/γ-Al2O3 and the subsequent reduction in H2 gave back CeAlO3/γ-Al2O3. TEM studies showed CeAlO3 crystallites growth on γ-Al2O3 and the oxidized sample showed CeO2 formation over CeAlO3, which in turn interfaced with γ-Al2O3 phase. XPS analysis of CeAlO3/γ-Al2O3 phase showed the presence of Ce in +3 and +4 state indicating surface oxidized CeAlO3 phase. Epitaxial relation for growth of CeAlO3 over γ-Al2O3 and CeO2 over CeAlO3 is demonstrated in the study, where adhesion of CeO2 over γ-Al2O3 is via CeAlO3 phase at the interface.