Publication

Abstract : The formation characteristics of CuAl2O4 from sol–gel boehmite doped with Cu2+ion and also the effect of dopants like Cu2+, Ti4+ and Ce4+ on calcination and concentration dependent structural evolution of α-Al2O3 from xerogels derived from boehmite sol are studied. The structural evolutions of various phases are studied by PXRD, FTIR, UV–vis (diffused reflectance) and {EPR} spectral techniques. Even though the formation temperature of α-Al2O3 from undoped boehmite is around 1200 °C, we observed significantly early and quantitative conversion of boehmite into α-Al2O3 along with the formation of CuAl2O4 spinel at 1000 °C in 4 and 8 mol.% Cu2+ ion doped samples owing to the nucleation effect and growth process initiated by the in situ generated spinel phase. However, no indication of such quantitative conversion in the case of 2% doped sample is seen presumably because of the retarding effect of transition aluminas on spinel formation. Temperature dependent phase evolution of CuAl2O4 spinel could be monitored by diffuse reflectance, {EPR} and PXRD, which show some interesting features associated with the change from CuO6 to CuO4 polyhedra. Dopants like Ti4+ and Ce4+ do not show any nucleation and facilitation effects in the formation of α-Al2O3 from boehmite xerogels.