Synthesis And Thermoelectric Properties Of Ag And Ga Doped PbTe Compound

Lead telluride compounds areⅣ-Ⅵnarrow band-gap (0.3ev) semiconductors which possess an average NaCl crystal structure. It is one of excellent thermoelectric materials in intermediate temperature range (500K～800K) which combines a set of desirable features, e.g. isotropic morphology, high crystal symmetry, low lattice thermal conductivity. Optimising the thermoelectric performance of PbTe compounds by choosing proper dopants have been the target of widespread investigations around the world for several years.Preparation method of single-phase Ga&Ag doped and codoped PbTe compounds were explored in this paper. The influences of Ga, Ag -doping on the structure and thermoelectric properties of PbTe compounds were investigated systematically. Meanwhile, we also investigated the influences of the preparation craft on the thermoelectric properties of Ag_0.01Ga_xPb_0.99-xTe compounds. Research results indicate that:For n-type Ga_xPb_1-xTe (x=0.01～0.05) compounds, the temperature dependent carrier concentration increased while the hall mobility decreased with increased Ga content, and the carrier scattering mechanism gradually changed from an acoustical phonon scattering to the interaction between an acoustical phonon and an ionized impurity scattering as x increased. The absolute Seebeck coefficient values decreased and the electrical conductivity increased significantly with increasing Ga content. The thermal conductivity decreased with rising temperature, and show a minimum, value when x is 0.03. Ga0.02Pb0.98Te compound reached a maximum ZT value of 1.25 at 673K.For Ag_xPb_1-x Te (x=0.002～0.05) compounds, in the whole measuring temperature range, the electrical conductivity increased first and then decreased with rising temperature, which is consistent with the case for a typical semiconductor. The sample had negative Seebeck coefficient which indicated n-type conductivity when x=0.01, the other ones who had Seebeck coefficient positive were p type. The content of Ag determined the conductivity properties of (AgGa)_xPb_1-2xTe (x=0.01～0.05) compounds, when the content of Ag was 1at%,the samples showed n type conduct while other ones show p type when x exceeded 0.01. In all quaternary samples, Ag_yGa_0.01Pb_0.99-yTe (y=0.01～0.05) samples were single phase while the Ag_0.01Ga_xPb_0.99-xTe (x=0.01～0.05) samples showed the better properties than other ones. The maximum ZT value of 1.33 was obtained at 675K for Ag_0.01Ga_0.01Pb_0.98Te compound.