Magnetocaloric and thermoelectric properties of two-phase composite Eu8Ga15.25Ge30.75

A novel Eu8Ga15.25Ge30.75 composite clathrate with alpha and 13 phases coexisting were synthesized for the first time. The composite exhibits two consecutive magnetic transitions at temperatures of 12 and 32 K corresponding to the TC of alpha and 13 phases, respectively. The magnetic entropy change with temperature reveals two distinct peaks, resulting in a broader -ASM(T) curve and an enhanced magnetic refrigeration capacity compared to single phase clathrate. Furthermore, the interactive growth of the alpha and 13 phases in the composite acts to reduce the lattice thermal conductivity. Specifically, at 600 K, the lattice thermal conductivity kappa L reaches its minimum value of 0.39 W/m center dot K. The zT value increases from 0 to 0.24 as the temperature ranges from 2 to 773 K.