Effect of citrate to nitrate ratio on the sol-gel synthesis of nanosized α-Al2O3 powder

This paper studied the effect of the variation of citrate to nitrate ratio on the sol-gel synthesis of nanocrystalline α-alumina powder. The process involves the formation of a sol using aluminium nitrate and citric acid which then transferred to a transparent gel and finally to a powdery mass. The prepared alumina powder was thoroughly characterised by different techniques such as phase analysis, thermal analysis, microstructure study, etc. Variation in citrate to nitrate molar ratio (C/N) influenced the thermal decomposition behaviour, particle size distribution, phase transformation temperature and specific surface area of the developed powder. The complete formation of α- Al2O3 was obtained at around 950 °C for C/N=1.5. The unimodal distribution of the particles within a narrow size range and higher particle to particle linking through solid bridging are the characteristics of the powder prepared at C/N=1.5. It was found higher citrate to nitrate ratio in the fuel rich condition is responsible for better properties of synthesised alumina powder.