High temperature x-ray diffraction study on phase transformation and lattice thermal expansion of mercury indium telluride crystals

The high temperature properties of Hg_(3-3x)In _2xTe₃ (MIT) (x = 0.5) crystals grown by the vertical Bridgman method were investigated. The high temperature x-ray diffraction patterns between 25 and 300 °C indicated that an order-disorder phase transformation happens at ∼290 °C. The mean thermal expansion coefficient of MIT crystal between 25 and 300 °C was calculated from the lattice parameter data to be 11.35 × 10^-6 °C^-1. The lattice parameters of MIT crystals were found to increase approximately linearly with temperature between 50 and 250 °C, but increased rather more rapidly between 250 and 300 °C and much more rapidly between 25 and 50 °C. The density of MIT crystal decreases from 6.248 g cm^-3 at 25 °C to 6.189 g cm^-3 at 300 °C with increasing temperature.