Temperature behavior of thermal expansion anisotropy, Grüneisen parameters and thermal conductivity of chalcopyrite AgGa0.7In0.3Se2 crystal

Abstract

Thermal expansion coefficients measurements of AgGa0.7In0.3Se2 with the direction of c- and a-axis are made in the temperature range between 300 and 900 K. It is obviously that AgGa0.7In0.3Se2 is with a reverse thermal expansion behavior along the c-axis, and variation of directional coefficient at different temperatures as a function of cos2φ has been discussed in this work. It’s found that the crystal would expand with increasing temperature if the angle between the direction [hkl] and the c-axis is greater than 42.71°. In addition, Grüneisen parameters at different temperatures have been calculated and also exhibit anisotropic behavior (γa > γc). At last, by a modified formula, variation of lattice thermal conductivity with temperature have been deduced. And the calculation value at room temperature is a little larger than the measurement value of thermal conductivity with [100] direction at room temperature which is found to be 0.751 W/m K.