Thermoelectric (TE) materials, which can realize directly and reversibly conversion between heat and electricity, have been widely utilized to the area of power generation, refrigeration and waste-heat recovery [1-3]. In order to improve TE conversion efficiency, efforts should be made to develop new TE materials or optimize available materials. Generally speaking, the comprehensive performance of a TE material is described by the dimensionless figure of merit ZT=S2T/κ, where S is the Seebeck coefficient, is the electrical conductivity, T is the absolute temperature, and κ is the total thermal conductivity which is the sum of the electronic (κel) and lattice (κlatt) contributions at a certain absolute temperature T [1-6].