Highly anisotropic crystal growth and thermoelectric properties of K2Bi8ÀxSbxSe13 solid solutions: Band gap anomaly at low x

The thermoelectric properties of solid solutions of the type b-K2Bi82xSbxSe13 (0,x,8) were studied with respect to thermal behavior, band gap variation, and charge transport properties as a function of x. At x values between 0 and 1.5, the energy band gap is observed to decrease ~anomalous! before it widens with increasing x values as would be expected. For selected members of the solid solutions, the Bridgman technique was applied to obtain well-grown oriented ingots that were used to measure the thermal conductivity and charge transport properties in different growth directions. The measurements showed a strong anisotropy in thermoelectric properties with the largest anisotropy observed in the electrical conductivity. Lattice thermal conductivities of the selected solid solutions were observed to decrease when the x value increases. Preliminary doping studies on the x51.6 member were carried out and it was shown that it is possible to significantly increase the power factor. © 2002 American Institute of Physics. @DOI: 10.1063/1.1481967#