Influence of citric acid to aluminium nitrate molar ratio on the combustion synthesis of alumina–zirconia nanopowders

The precursor for combustion synthesis was a mixed citrate/nitrate gel prepared from aluminium nitrate, zirconium oxychloride and citric acid. The combustion synthesis of this gel produces nanometer-sized zirconia–alumina nanopowder. The influence of citrate/aluminium nitrate molar ratio of the precursor on the combustion rate and phase transformation was investigated. The α-Al2O3 phase transformation temperature differs with the citrate/aluminium nitrate molar ratios. X-ray diffraction analysis shows that the phases present at 1200 °C are α-Al2O3 and t-ZrO2 irrespective of initial citrate/aluminium nitrate molar ratio. TEM micrograph of calcined powder revealed that the particles size is significantly influenced by the citrate/aluminium nitrate molar ratio. EDAX confirms the presence of alumina and zirconia particle in the nanopowder calcined at 1200 °C.