用高温 X 射线衍射仪对锂蒙脱石粘土进行实验,阐明锂蒙脱石处在不同温度时晶体结构发生的变化情况及其相变温度,以及所产生的相变物相及其形成的最佳温度。实验结果显示锂蒙脱石的相变温度在800℃左右。当温度继续增加,样品中产生新的...用高温 X 射线衍射仪对锂蒙脱石粘土进行实验,阐明锂蒙脱石处在不同温度时晶体结构发生的变化情况及其相变温度,以及所产生的相变物相及其形成的最佳温度。实验结果显示锂蒙脱石的相变温度在800℃左右。当温度继续增加,样品中产生新的物相——μ—堇青石,900℃左右是堇青石形成的最佳温度。展开更多
A series of solid solutions Er2W3-xMoxO12(0.5≤x≤2.5)were successfully synthesized by the solid state method.Their crystal structures and negative thermal expansion properties were studied by high temperature X-ray p...A series of solid solutions Er2W3-xMoxO12(0.5≤x≤2.5)were successfully synthesized by the solid state method.Their crystal structures and negative thermal expansion properties were studied by high temperature X-ray powder diffraction and the Rietveld method.All samples with rare earth tungstates and molybdates crystallize in the same orthorhombic structure with space group Pnca,and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure.Thermal expansion coefficients(TECs)of Er2W3-xMoxO12 were determined as-16.2×10 -6K -1for x=0.5 and-16.5×10 -6 K- 1for x=2.5 while-20.2×10 -6K -1and-18.4×10 -6K -1 for unsubstituted Er2W3O12 and Er2Mo3O12 in the identical temperature range of 200-800℃.High temperature XRD data and bond length analysis suggest that the difference between W-O and Mo-O is responsible for the change of TECs after the element substitution in the series of solid solutions.展开更多
基金Project(20080430556)supports by China Postdoctoral Science Foundation
文摘A series of solid solutions Er2W3-xMoxO12(0.5≤x≤2.5)were successfully synthesized by the solid state method.Their crystal structures and negative thermal expansion properties were studied by high temperature X-ray powder diffraction and the Rietveld method.All samples with rare earth tungstates and molybdates crystallize in the same orthorhombic structure with space group Pnca,and show the negative thermal expansion phenomena related to transverse vibration of bridging oxygen atoms in the structure.Thermal expansion coefficients(TECs)of Er2W3-xMoxO12 were determined as-16.2×10 -6K -1for x=0.5 and-16.5×10 -6 K- 1for x=2.5 while-20.2×10 -6K -1and-18.4×10 -6K -1 for unsubstituted Er2W3O12 and Er2Mo3O12 in the identical temperature range of 200-800℃.High temperature XRD data and bond length analysis suggest that the difference between W-O and Mo-O is responsible for the change of TECs after the element substitution in the series of solid solutions.
