Effect of anion and cation substitution in tungsten disulfide and tungsten diselenide on conductivity and thermoelectric power

The temperature dependences of the conductivity and thermoelectric power for a series of samples W$_{1-x}$Nb$_{x}$S$_{2}$, W$_{1-x}$Nb$_{x}$Se$_{2}$, WS$_{2-y}$Se$_{y}$, W$_{1-x}$Nb$_{x}$S$_{2-y}$Se$_{y}$ are studied at low temperatures. It is found that the cation substitution of W atoms with Nb leads to an increase in the conductivity and a decrease in the thermoelectric power. The anion substitution of S with Se atoms results in a simultaneous increase in the conductivity and thermoelectric power. The highest power factor among the samples studied is inherent to W$_{0.8}$Nb$_{0.2}$Se$_{2}$.