Mechanical strength and thermoelectric performance in metal chalcogenide MQ (M=Ge,Sn,Pb and Q=S, Se, Te) based compositions
View Patent ↗Thermoelectric eutectic and off-eutectic compositions comprising a minor phase in a thermoelectric matrix phase are provided. These compositions include eutectic and near eutectic compositions where the matrix phase is a chalcogenide (S, Se, Te) of Ge, Sn, or Pb or an appropriate alloy of these compounds and at least one of Ge, Ge 1−x Si x , Si, ZnTe, and Co are precipitated as the minor phase within the matrix. Methods of making and using the compositions are also provided. The thermoelectric and mechanical properties of the compositions make them well-suited for use in thermoelectric applications. Controlled doping of eutectic compositions and hypereutectic compositions can yield large power factors. By optimizing both the thermal conductivities and power factors of the present compositions, ZT values greater than 1 can be obtained at 700K.
1. A composition comprising:
(a) a matrix comprising a compound having the formula MQ, wherein M is Ge, Sn, Pb or a combination thereof and Q is S, Se, Te or a combination thereof;
(b) a minor phase comprising an alloy of Ge and Si ZnTe, Co or a combination thereof; and
(c) a dopant;
wherein the minor phase is dispersed in the matrix.
2. The composition of claim 1 having a ZT of at least 1 at 700 K.
3. The composition of claim 1 , wherein the composition comprises a eutectic mixture of the matrix and the minor phase.
4. The composition of claim 1 , wherein the matrix comprises PbTe and the minor phase comprises an alloy of Ge and Si.
5. The composition of claim 4 , wherein the alloy of Ge and Si is present in an amount of about 2 to about 30 mol. %, based on the total amount of the matrix and minor phase.
6. The composition of claim 1 , wherein the minor phase comprises Ge (1−x) Si x and x has a value in the range from 0.15 to 0.25.
7. The composition of claim 6 having a ZT at least 1 at 700 K.
8. The composition of claim 1 having a Vickers hardness of at least 0.4 GPa.
9. The composition of claim 1 , wherein the minor phase comprises an alloy of Ge and Si.
10. The composition of claim 1 , wherein the minor phase comprises ZnTe.
11. The composition of claim 1 , wherein the minor phase comprises Co.
12. A composition comprising:
(a) a matrix comprising a compound having the formula MQ, wherein M is Ge, Sn, Pb or a combination thereof and Q is S, Se, Te or a combination thereof;
(b) a minor phase comprising Ge (1−x) Si x , ZnTe, Co or a combination thereof; and
(c) a dopant;
wherein the minor phase is dispersed in the matrix and x has a value from 0 to 1, and further
wherein the composition comprises a hypereutectic mixture of the matrix and the minor phase.
13. A composition comprising:
(a) a matrix comprising a compound having the formula MQ, wherein M is Ge, Sn, Pb or a combination thereof and Q is S, Se, Te or a combination thereof;
(b) a minor phase comprising Ge (1−x) Si x , ZnTe, Co or a combination thereof; and
(c) a dopant;
wherein the minor phase is dispersed in the matrix and x has a value from 0 to 1, and further wherein the dopant is PbI 2 .
14. The composition of claim 13 , wherein x =0, the composition comprising a eutectic mixture of the PbTe and the Ge and having a ZT of at least 0.6 at 675 K.
15. The composition of claim 13 , wherein x =1, the composition comprising a hypereutectic mixture of the PbTe and the Si and having a ZT of at least 0.8 as 675 K.
16. A composition comprising:
(a) a matrix comprising a compound having the formula MQ, wherein M is Ge, Sn, Pb or a combination thereof and Q is S, Se, Te or a combination thereof; and
(b) a minor phase comprising Ge( i-x )Si x ;
wherein the Ge (1−x) Si x is dispersed in the matrix and x has a value in the range from 0.05 to 0.95.
17. The composition of claim 16 , wherein the matrix comprises PbTe and the Ge (1−x) Si x is present in an amount of about 2 to about 30 mol. %, based on the total amount of the matrix and minor phase.
18. The composition of claim 16 having a Vickers hardness of at least 0.4 GPa.
19. A method of making a composition, the method comprising combining a compound having the formula MQ, wherein M is Ge, Sn, Pb or a combination thereof and Q is S, Se, Te or a combination thereof, with Ge (1−x) Si x , ZnTe, Co or a combination thereof, and a dopant under vacuum and heating the combination at a temperature and for a time sufficient to form a composition comprising a minor phase of Ge (1−x) Si x , ZnTe, Co or a combination thereof dispersed in a matrix of the compound having the formula MQ, wherein x has a value from 0 to 1.
20. The method of claim 19 , wherein the composition comprises a eutectic mixture of the matrix and the minor phase.
21. The method of claim 19 , wherein the composition comprises a hypereutectic mixture of the matrix and the minor phase.
22. The method of claim 19 , wherein the matrix comprises PbTe, the minor phase comprises Ge (1−x) Si x , and the Ge (1−x) Si x is present in an amount of about 2 to about 30 mol. %, based on the total amount of the matrix and minor phase.
23. A method for power generation comprising placing a composition in thermal contact with a heat source whereby the composition generates electricity and powering an electrical device with the electricity, the composition comprising:
(a) a matrix comprising a compound having the formula MQ, wherein M is Ge, Sn, Pb or a combination thereof and Q is S, Se, Te or a combination thereof;
(b) a minor phase comprising Ge (1−x) Si x , ZnTe, Co or a combination thereof; and
(c) a dopant;
wherein the minor phase is dispersed in the matrix and x has a value from 0 to 1.