Y_2Hf_2O_7 and Lu_2Hf_2O_7 precursor powders are prepared by nitrate solution combustion method with various fuels at 450℃, respectively. Phase evolution of the synthesized powders was determined by X-ray diffraction (XRD) techniques. Single-phase cubic Y_2Hf_2O_7 and Lu_2Hf_2O_7 crystalline powders were obtained by calcining the resultant combustion ash at 800℃ for 2h. By controlling the pH of the nitrate solution, the type of fuel and the ratio of fuel/nitrate, nanosized powders can be obtained. The crystallite size of resultant powders is much related to the combustion flame temperature, which can be controlled by controlling the type of fuel and adjusting the fiiel-to-oxidizer ratio. The influence of the ratio of reactants and the type of fuel on the properties of the final products was investigated. The crystal size and morphology were analyzed by TEM.
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