The Effect Of Doping Of Elements Such As Zn And Ga On The Thermoelectric Properties Of ?-Cu 2 Se

As the world's environment and the increasingly serious energy crisis, green environmental protection of the thermoelectric material was attached great importance. Recently, Cu₂ Se based thermoelectric material is a hot area of research due to the good thermoelectric properties. In this work, the crystal strucutre and thermoelectric properties of 1.0 at.% Zn, Gd, Ga, Cd or Co doped Cu₂ Se were researched primarily, and then the effect of Zn or Ga doping content on the crystal structure and thermoelectric properties of Cu₂ Se were studied in detail.?1? The crystal structure of Zn, Gd, Ga, Cd or Co doped Cu₂ Se still keep the crystal structure of Cu₂ Se. Doping of Ga, Cd or Zn not only optimized power factor by reducing the resistivity, but also reduced the lattice thermal conductivity through lattice distortion; higher ZT value of 1.01, 0.94, 0.98 has achieved comparing to the undoped sample at 773 K, respectively. However, the ZT value slightly reduced to 0.83 or 0.77 by doping of Co or Gd at 773 K.?2? The dense microstructure and uniform composition distribution are found in SPS sintered Cu_2-xZn_xSe?x = 0,0.0025,0.005,0.0075,0.01,0.015,0.02? samples with grain size of about 20?m. The solubility of Zn in Cu₂ Se is about 1.2 at.%, Zn Se phase is found when the Zn content is higher than the solubility. An appropriate amount of Zn doping could optimize the power factor by lowering the resistivity and reducing the thermal conductivity. The second phase of Zn Se will increase thermal conductivity, and then reducing the ZT value. When x = 0.0075, the ZT value of 1.11 bulk sample has achieved at 773 K, which is 19.9% improvement than the undoped sample.?3? In Cu_2-xGa_xSe?x = 0,0.0025,0.005,0.0075,0.01? systems, a small amount of doped Ga can be completely dissolved in the Cu₂ Se compound. When the content of Ga reached the upper solution limit of Ga, exceeding Ga will form the second phase of Cu Ga Se₂. An appropriate doping content of Ga could lower the resistivity of Cu₂ Se to optimize power factor, and reduce obviously the thermal conductivity. The existance of Cu Ga Se₂ second phase will increase thermal conductivity. The higher ZT value of Cu1.9925Ga0.0075 Se alloy have obtained the increase of 28% as compared to the pure sample, which achieved about 1.13 at 773 K.