Electrical Properties and Phase Changes in Ru_2Si_3 and Re_4Si_7

摘要

Ruthenium sesquisilicide (Ru_2Si_3) and Rhenium heptasilicide (Re_4Si_7) are two semiconducting silicides that are of technological interest for their thermoelectric properties. Both Ru_2Si_3 and Re_4Si_7 undergo phase transformations upon cooling that alter the microstructure of initially single-crystal material. The effect of these transformed microstructures on the electrical properties important for thermoelectric materials (electrical resistivity ρ and Seebeck coefficient α) for these two compounds is examined. Both Ru_2Si_3 and Re_4Si_7 have differences in α that are dependent on the crystal structure, while the transformation-induced microstructure of Re_4Si_7 strongly affects the directional dependence of ρ.