Potassium sodium niobate （KNN） powders were synthesized by a modified sol-gel method, using as starting chemicals potassium carbonate, sodium carbonate, and niobium hydroxide, and, as esterification and chelating ag...Potassium sodium niobate （KNN） powders were synthesized by a modified sol-gel method, using as starting chemicals potassium carbonate, sodium carbonate, and niobium hydroxide, and, as esterification and chelating agents, respectively, ethylene glycol （EG） and ethylene diamine tetraacetic acid （EDTA）/citrate. The effects of citric acid （CA）, EG, and EDTA on the stability of the precursor sol were systemically inves-tigated. The powders and gels were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis-differential scanning calorimetry （TGA-DSC）. The results indicated that a stable precursor sol was formed when n（CA）：n（Mn＋）= 3：1, n（EDTA）：n（NH4OH） = 1：3.5, and n（CA）：n（EG） = 1：2. The xerogel was calcined at 500-950 ℃ to prepare the KNN powder. Pure KNN perovskite phase with a cube-like structure was synthesized at 850 ℃ from the precursor sol for a K/Na molar ratio of 1.2. The formation mechanism of the KNN perovskite phase was also discussed.展开更多
基金supported by the National Natural Science Foundation of China(NSFC No.51172108)Program for Changjiang Scholars and Innovative Research Teams in Universities(IRT0968)+2 种基金Program for New Century Excellent Talents in Universities(NCET10-0070)a project funded by the Priority Academic Program Development of Jiangsu Higher Education InstitutionsNanjing University of Aeronautics and Astronautics Research Fund for Fundamental Research(NJ2010010,NZ2010001)
文摘Potassium sodium niobate （KNN） powders were synthesized by a modified sol-gel method, using as starting chemicals potassium carbonate, sodium carbonate, and niobium hydroxide, and, as esterification and chelating agents, respectively, ethylene glycol （EG） and ethylene diamine tetraacetic acid （EDTA）/citrate. The effects of citric acid （CA）, EG, and EDTA on the stability of the precursor sol were systemically inves-tigated. The powders and gels were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis-differential scanning calorimetry （TGA-DSC）. The results indicated that a stable precursor sol was formed when n（CA）：n（Mn＋）= 3：1, n（EDTA）：n（NH4OH） = 1：3.5, and n（CA）：n（EG） = 1：2. The xerogel was calcined at 500-950 ℃ to prepare the KNN powder. Pure KNN perovskite phase with a cube-like structure was synthesized at 850 ℃ from the precursor sol for a K/Na molar ratio of 1.2. The formation mechanism of the KNN perovskite phase was also discussed.
