Effects of Sm Doping to Improve the Thermoelectric Properties of ZnO Ceramics

A series of Sm doped ZnO based thermoelectric materials were prepared by mechanical alloying and spark plasma sintering. The effects of Sm doping on ZnO based thermoelectric materials were systematically studied by means of electrical and thermal properties tests combined with first principles calculations of energy band, density of states and elastic constants. The experimental results show that the substitution of Sm at Zn site could cause the valence band and conduction band moving down, and the 4f orbitals of Sm could contribute to the increase of the density of states near the Fermi level, corresponding to the increase of carrier concentration and electrical conductivity. The substitution of Sm at Zn site could cause the decrease of effective mass and Seebeck coefficient. The substitution of Sm at Zn site could lead to the decrease of Young's modulus and lattice thermal conductivity, which contribute to the decrease of thermal conductivity. Finally, the highest dimensionless thermoelectric figure of merit (ZT) value has been increased to 0.346, which is 3.48 times as pristine ZnO.