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 αa and average volume thermal expansion coefficient αV of CoSi are 1.14×10-5 K-1 and 3.42×10-5 K-1, respectively, and they obey the law of 3αa=αV 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 αa=0.96×10-5 K-1, αc=0.73×10-6 K-1 and αV=2.45×10-5 K-1, respectively, and they obey the law of 2αa+αc=αV for hexagonal lattice. The expansions of CrSi2 along a axis are much larger than that along c axis, so it appeared strong anisotropy.