Mild Hydrothermal Synthesis, Characterization and Properties of Na_5Ce(PO_4)_3, Na_3Yb_2(PO_4)_3·H_2O and Na_(5-2x)Yb_2xCe_(1-x)(PO_4)_3·yH_2O  

作　　者：XU Yao-hua, WANG Dan, FENG Shou-hua, PANG Wen-qin and YUE Yong (Key Laboratory of Inorganic Synthesis & Preparative Chemistry, Jilin University, Changchun 130023, P. R. China Wuhan Institute of Physics, Academia Sinica, Wuhan 430071, P. R. China) 

出　　处：《Chemical Research in Chinese Universities》2000年第4期287-300,共14页高等学校化学研究（英文版）

基　　金：Supported by the National Natural Science Foundation of China.

摘　　要：Novel phosphates, Na5-2x Yb2xCe1-x (PO4)3·yH2O(x=0-1, y=0-1), were synthesized under mild hydrothermal conditions at 240℃ with Ce(SO4)2·H2O, Ce(SO4)2·2(NH4)2SO4· 4H2O, CeO2, Yb2O3, 85 % H3PO4 and NaOH as the starting materials. The products were sensitively influenced by the pH value of the systems and reaction temperature. Under an acidic condition, CePO4 was the product at 240℃, in which Ce(Ⅳ ) species was reduced to Ce(Ⅲ) species. Under a weak basic condition, Na2Ce(PO4)2·0. 79H2O was produced. Under a medium basic condition, the expected compound Na5Ce(PO4)3 was the product. Under a basic condition, CeO2 was the final product, amorphous phase was also produced in some cases. The structure of the compounds were investigated by X-ray diffraction, SEM, IR, Raman, 31P MAS NMR and XPS spectroscopies. To determine the valence of Ce in the compound, EPR and DRS of the compound were also recorded. The thermal properties of the compounds were determined with DTA-TG analysis. Na5Ce(PO4)3 was decomposed into Na3Ce(PO4)2, Na4P2O7 and O, at 694℃, in which Ce(Ⅳ) was reduced to Ce(Ⅲ) species. Na3Yb2(PO4)3·H2O lost water and was transferred into a new phase at a high temperature 682℃. The thermal stability of Na5-2xYb2xCe1-x (PO4)3· yH2O could be improved by increasing x value. When x=0. 54, the compound was stable even at the temperature ca. 1 000℃.The ionic conductivities of the compounds were increased when the amount of Yb in the compound was increased and when x=0. 33, it reached the highest value (σ300℃= 3. 96 ×10-6 S·cm-1).Novel phosphates, Na5-2x Yb2xCe1-x (PO4)3·yH2O(x=0-1, y=0-1), were synthesized under mild hydrothermal conditions at 240℃ with Ce(SO4)2·H2O, Ce(SO4)2·2(NH4)2SO4· 4H2O, CeO2, Yb2O3, 85 % H3PO4 and NaOH as the starting materials. The products were sensitively influenced by the pH value of the systems and reaction temperature. Under an acidic condition, CePO4 was the product at 240℃, in which Ce(Ⅳ ) species was reduced to Ce(Ⅲ) species. Under a weak basic condition, Na2Ce(PO4)2·0. 79H2O was produced. Under a medium basic condition, the expected compound Na5Ce(PO4)3 was the product. Under a basic condition, CeO2 was the final product, amorphous phase was also produced in some cases. The structure of the compounds were investigated by X-ray diffraction, SEM, IR, Raman, 31P MAS NMR and XPS spectroscopies. To determine the valence of Ce in the compound, EPR and DRS of the compound were also recorded. The thermal properties of the compounds were determined with DTA-TG analysis. Na5Ce(PO4)3 was decomposed into Na3Ce(PO4)2, Na4P2O7 and O, at 694℃, in which Ce(Ⅳ) was reduced to Ce(Ⅲ) species. Na3Yb2(PO4)3·H2O lost water and was transferred into a new phase at a high temperature 682℃. The thermal stability of Na5-2xYb2xCe1-x (PO4)3· yH2O could be improved by increasing x value. When x=0. 54, the compound was stable even at the temperature ca. 1 000℃.The ionic conductivities of the compounds were increased when the amount of Yb in the compound was increased and when x=0. 33, it reached the highest value (σ300℃= 3. 96 ×10-6 S·cm-1).

关 键 词：CERIUM Ionic conduction Mild hydrothermal synthesis Rare earth phosphate YTTERBIUM 

分 类 号：O614[理学—无机化学]