PREPARATION AND THERMAL EXPANSION OF FE2-xYxW3O12 POWDER BY CITRATE SOL-GEL PROCESS |
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| Authors: | Haijun Zhang Qing Zhang Honglin Du Quanli Jia |
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| Affiliation: | 1. High Temperature Ceramics Institute, Zhengzhou University , Henan, China zhanghaijun@zzu.edu.cn;3. High Temperature Ceramics Institute, Zhengzhou University , Henan, China;4. School of Physics, Peking University , Beijing, China |
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| Abstract: | Fe2-xYxW3O12 powder has been synthesized by the citrate sol-gel process. A model was proposed to calculate the concentration of species in a citric solution. The calculated results could provide valuable information for determining the optimal molar ratio of cation to citric acid and pH value of solution for Fe2-xYxW3O12 preparation. The predicted parameters derived from this model are in good agreement with the experimental results. The prepared gel and the Fe2-xYxW3O12 powder were characterized by X-ray diffraction (XRD) and differential thermal analysis-thermogravimetry (DTA-TG). The results show that it is very difficult to obtain pure Fe2W3O12 powder by the citrate sol-gel process in the temperature range 500°–1000°C, however, Y2W3O12 can easily be prepared even at 500°C. Y2W3O12 annealed at 1000°C for 10 h is favorable for absorbing moisture in air to form Y2W3O12·3.3H2O. The thermal expansion coefficients of Y2W3O12·3.3H2O are: αa = ? 8.01 × 10?6°C?1, αb = ? 2.51 × 10?7°C?1, and αc = ? 5.55 × 10?6°C?1 in 473–1173 K. |
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| Keywords: | Fe2-xYxW3O12 Negative expansion materials Sol-gel |
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