热电材料CoSi和CrSi_2的晶格热膨胀性

利用动态高温X射线衍射技术分别对立方CoSi和六方CrSi2化合物在298~973 K温度范围内的晶格热膨胀性进行了研究。结果表明:化合物CoSi的点阵参数随温度升高呈线性增长关系,其平均线热膨胀系数aα和平均体热膨胀系数αV分别为1.14×10-5K-1和3.42×10-5K-1,两者之间符合立方晶系关系式,即3αa=αV;化合物CrSi2的点阵参数随温度升高而显著增大,其中沿a轴和c轴的平均线热膨胀系数及平均体热膨胀系数分别为αa=0.96×10-5K-1,cα=0.73×10-6K-1和αV=2.45×10-5K-1,三者之间符合六方晶系关系式,即2αa+cα=αV;化合物CrSi2沿a轴方向的线热膨胀系数远大于沿c轴方向的,呈较强的各向异性。

Lattice Thermal Expansion Properties of Thermoelectric Materials CoSi and CrSi2

The lattice thermal expansion properties of compounds CoSi and CrSi2 were determined by means of dynamic high temperature X-ray diffraction（HTXRD） in the temperature range of 298-973 K. The results show that the lattice parameters of CoSi increase linearly with the increase of temperature. The average linear thermal expansion coefficient a. and average volume thermal expansion coefficient av of CoSi are 1.14×10^-5 K^-1 and 3. 42×10^-6 K^-1 , respectively, and they obey the law of 3 aa =av for cubic lattice. The lattice parameters of CrSi2 increase progressively with the increase of temperature. The average linear thermal expansion coefficients and average volume thermal expansion coefficient of CrSi2 are aa =0. 96×10^-5K^-1, ac=0. 73×10^-6 K^-1 and av = 2. 45×10^-5 K^-1, respectively, and they obey the law of 2 aa＋ac=av for hexagonal lattice. The expansions of CrSi2 along a axis are much larger than that along c axis, so it appeared strong anisotropy.