THERMOELECTRIC PROPERTIES OF PbSe-AgSbSe₂ SOLID SOLUTIONS

Lead chalcogenides based on PbX, (X=S, Se, Te), widely used as functional materials thermoelectricity. One way to expand and improve the parameters of thermoelectric devices based PbX (X = S, Se, Te) is the use of solid solutions.

For the synthesis of alloys PbSe–AgSbSe₂ used simple matter of high purity: Ag – 99,99%; Sb – 99,999%; Pb – 99,999%,Se – 99,999% main component. Solubility based on PbSe and AgSbSe₂ for determined X-ray and differential thermal analysis. For the growth of single crystals of solid solutions of PbSe-AgSbSe₂ used horizontal Bridgman method. Single crystals of the solid solution based on PbSe corresponded component composition 0, 5, 8 mol% AgSbSe₂. Single crystals of the solid solution based on component composition AgSbSe₂ corresponded 0, 10, 20, 30 and 40 mol% PbSe. Samples of 50 mol% PbSe were two-phase. Within the investigated solid solutions the dependence of the period of the unit cell of the composition of the solid solution. For example, for solid solutions based on PbSe she was in the range of a = 0.6126 nm, for PbSe, to a = 0.6000 nm for sample containing with 10 mol% AgSbSe₂, and the unit cell volume of V = 0,230 nm³ to V = 0,227 nm³, respectively. In our opinion, this is due to the replacement of two Pb2+ into Ag+ and Sb+.

Basic electric and thermoelectric parameters we have studied solid solutions in the table.

 Electric and thermoelectric properties of PbSe-AgSbSe₂

The sign of the thermoelectric coefficient (α) determine type conductivity. Change of conductivity (σ) with the composition of the solid solution may be due to defects in the crystal lattice of single crystals. The maximum value of the thermoelectric power (α²σ) have crystals AgSbSe₂.

Because the quality factor has dimension K^-1, in practice use dimensionless figure of merit ZT, where T - the absolute temperature. For PbSe was 0.42. In the calculations it was considered that the thermal conductivity (χ_tot) ~ 1,2·10^-2 W/(K·cm). For AgSbSe₂ calculated values ​​ZT≈2,2·10^-2, with a coefficient χ_tot≈0,6·10^-2 W/(K·cm)

Literature

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