Thermal expansion and thermal conductivity of In$_2$S$_3$ and CuIn$_5$S$_8$ compounds and (CuIn$_5$S$_8$)$_{1-x}$(In$_2$S$_3$)$_x$ alloys

Thermal expansion and thermal conductivity are studied in the respective temperature ranges 80–600 and 300–600 K for In$_2$S$_3$ and CuIn$_5$S$_8$ single-crystal compounds and (CuIn$_5$S$_8$)$_{1-x}$(In$_2$S$_3$)$_x$ alloys grown by planar crystallization of the melt (the vertical Bridgman method). From the data, the thermal-expansion coefficient $\alpha_L$ is calculated. The dependences of the thermal-expansion coefficient $\alpha_L$ and the thermal conductivity $\chi$ on the composition parameter $x$ are constructed. It is established that $\alpha_L$ linearly varies with $x$, whereas $\chi$ has a minimum at intermediate values of $x$.