Thermoelectric properties of Mn-doped Ru2Si3

Pure and Mn-doped single crystals of ruthenium silicide (Ru₂Si₃) have been grown by floating zone technique with radiation heating in order to investigate the thermoelectric efficiency of this compound. Electrical resistivity, Hall effect, Seebeck coefficient and thermal conductivity of the crystals were measured at 100 - 900 K. Undoped crystals show in the thermoelectric power both types of conductivity. The Seebeck coefficient of Ru_1-xMn_xSi_1.5 is positive in the whole temperature range studied and reaches the maximum value of 450 μV/K at about 500 K. The room temperature value of 300 μV/K is twice higher in magnitude than the corresponding value for the undoped Ru₂Si₃. The charge carrier concentration in the 1% Mn-doped samples is about 10¹⁸cm^-3 at room temperature and the Hall mobility is about 20 cm²/V·s. The comparison with the undoped Ru₂Si₃ shows a twofold increase of the carrier mobility as the result of doping. The performed theoretical calculation of the carrier mobility is based on the effective masses, which are estimated from the ab initio electronic band structure and classical scattering mechanisms. The mobility as well as thermoelectric properties show a reasonable agreement with the experimental data for both Mn-doped and undoped Ru₂Si₃ crystals.