Electron transport properties of thermoelectrics based on layered substituted transition metal dichalcogenides

Resumo

Temperature dependences of the electrical conductivity are studied in the range 4.2’300 K and Seebeck coefficient at room temperature of bulk samples of tungsten dichalcogenide polycrystals with niobium substitutions for tungsten and selenium substitutions for sulfur – W_1–xNb_x(S_1–ySe_y)₂. The two-dimensionalization of electron transport properties is detected at niobium concentrations x ≥ 0.1 in W_1–xNb_xS₂ and x ≥ 0.05 in W_1–xNb_xSe₂. In samples with additional partial selenium substitution for sulfur the electron transport remains three-dimensional. At room temperature the Seebeck coefficient (at equal electrical conductivities) is several times higher in the samples with quasi-two-dimensional transport than in the samples with three-dimensional transport. The calculation of the power factor at room temperature shows its nine times increase.