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
|
№ |
mol. % PbSe |
Type conductivity |
σ, Оm -1∙cm-1 |
α, μW/K |
α2σ,10-6 W/m∙K2 |
|
1 |
100 |
р |
350 |
220 |
17 |
|
2 |
95 |
n |
33 |
60 |
0,12 |
|
3 |
92 |
р |
22 |
180 |
0,71 |
|
4 |
40 |
р |
0,01 |
1100 |
1,1 |
|
5 |
30 |
р |
0,02 |
940 |
2 |
|
6 |
20 |
р |
0,5 |
700 |
17 |
|
7 |
10 |
р |
0,9 |
650 |
37 |
|
8 |
0 |
р |
1,4 |
530 |
49 |
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.
We calculated thermoelectric figure of merit: Please use another browser to view contentBecause 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 (χtot) ~ 1,2·10-2 W/(K·cm). For AgSbSe2 calculated values ZT≈2,2·10-2, with a coefficient χtot≈0,6·10-2 W/(K·cm)
Literature
- Kumar R.S., Sekar A., Victor Jaya N., Natarajan S.Synthesis and high pressure studies of the semiconductor AgSbSe2.// J. Alloys Compd. № 1-2(285), 1999. – P. 48–50.
- Maksymilian Schmidt, Rafal Zybala, Krzysztof T. Wojciechowski. Structural and Thermoelectric Properties of AgSbSe2-AgSbTe2 System // Ceramic Materials. № 4(62), 2010. – P. 465–470.
- Growth mechanism and thermoelectric properties of PbTe/SnTe/PbTe heterostructures // E.I. Rogacheva, S.N. Grigorov, O.N. Nashchekina, [at al.] / Thin Solid Films – 2005. – Vol.493, №1-2. – P. 41–48.
- Rowe D. M. Handbook of thermoelectrics. / D. M. Rowe. – New. York : CRC Press, 1995. – 703 p
