Cr_2(WO_4)_3和Cr_2(MoO_4)_3的负热膨胀特性研究

Negative Thermal Expansion Property of Cr_2(WO_4)_3 and Cr_2(MoO_4)_3

用液相反应-前驱物烧结法制备了Cr2（WO4）3和Cr2（MoO4）3粉体。298～1073K的原位粉末X射线衍射数据表明Cr2（WO4）3和Cr2（MoO4）3的晶胞体积随温度的升高而增大，本征线热膨胀系数分别为（1．274±0.003）×10^-6K^-1和（1．612±0．003）×10^-6K^-1。用热膨胀仪研究了Cr2（WO4），和Cr2（MoO4），在静态空气中298～1073K范围内热膨胀行为，即开始表现为正热膨胀，随后在相转变点达到最大值，最后表现为负热膨胀，其负热膨胀系数分别为（-7．033±0．014）×10^-6K^-1和（-9．282±0．019）×10^-6K^-1。

Cr2（WO4）3 and Cr2（MoO4）3 powders were prepared by liquid phase reaction-precursor sintering method. in situ-powder X-ray diffraction data from 298 to 1 073 K shows an essentially linear increase in cell volume as a function of experimental temperature. The intrinsic linear coefficient of thermal expansion from these data is （1.274±0.003）×10^-6 K^-1 and （1.612±0.003）×10^-6 K^-1, respectively. Thermal expansion behavior of CrdWO4）3 and Cr2（MoO4）3 was studied in static air in the temperature range of 298 to 1073 K by a thermo-dilatometer. Two samples showed a positive thermal expansion in the beginning, followed by a phase transition and then a negative thermal expansion （NTE）. The negative thermal expansion coefficients （NTEC） of Cr2（WO4）3 and Cr2（MoO4）3 were （-7.033±0.014）×10^-6 K^-1 and （-9.282±0.019）×10^-6 K^-1, respectively.