Silver-containing thermoelectric compounds
View Patent ↗A thermoelectric material of the general formula Ag 1−X M m M′Q 2+m , wherein M is selected from the group consisting of Pb, Sn, Ca, Sr, Ba, divalent transition metals, and combinations thereof; M′ is selected from the group consisting of Bi, Sb, and combinations thereof; Q is selected from the group consisting of Se, Te, S, and combinations thereof; 8≦m≦24; and 0.01≦x≦0.7. In embodiments of the invention, the compositions exhibit n-type semiconductor properties. In preferred embodiments, x is from 0.1 to 0.3, and m is from 10 to 18. The compositions may be synthesized by adding stoichiometric amounts of starting materials comprising Ag, M, M′, and Q to a reaction vessel, heating the starting materials to a temperature and for a period of time sufficient to melt the materials, and cooling the reaction product at a controlled rate of cooling.
1. A semiconductor material having the general formula Ag 1−x M m M′Q 2+m , wherein:
(a) M is at least one element selected from the group consisting of Pb, Sn, Ca, Sr, Ba, divalent transition metals, and combinations thereof;
(b) M′ is at least one element selected from the group consisting of Bi, Sb, and combinations thereof;
(c) Q is at least one element selected from the group consisting of Se, Te, S, and combinations thereof; and
(d) 8≦m≦24, and 0.01≦x<1.
2. A semiconductor material according to claim 1 , wherein 0.05≦x≦0.6.
3. A semiconductor material according to claim 2 , wherein 0.1≦x≦0.3.
4. A semiconductor material according to claim 2 , wherein m≧10.
5. A semiconductor material according to claim 2 , wherein M is Pb.
6. A semiconductor material according to claim 2 , wherein M′ is Sb.
7. A semiconductor material according to claim 2 , wherein Q is Te.
8. A semiconductor material according to claim 2 , of the formula Ag 1−x Pb 10 M′Q 12 .
9. A semiconductor material according to claim 2 , of the formula Ag 1−x Pb 12 M′Q 14 .
10. A semiconductor material according to claim 2 , of the formula Ag 1−x Pb 14 M′Q 16 .
11. A semiconductor material according to claim 2 , of the formula Ag 1−x Pb 16 M′Q 18 .
12. A semiconductor material according to claim 2 , of the formula Ag 1−x Pb 18 M′Q 20 .
13. A thermoelectric material according to claim 2 which is substantially free of external dopants.
14. A process of manufacturing a conductive material of the formula Ag 1−x M m M′Q 2+m , wherein
(a) M is at least one element selected from the group consisting of Pb, Sn, Ca, Sr, Ba, divalent transition metals, and combinations thereof;
(b) M′ is at least one element selected from the group consisting of Bi, Sb, and combinations thereof;
(c) Q is at least one element selected from the group consisting of Se, Te, S, and combinations thereof; and
(d) 8≦m≦24, and 0.05≦x≦0.6;
said process comprising:
(1) adding stoichiometric amounts of starting materials comprising Ag, M, M′, and Q to a reaction vessel;
(2) heating said starting materials to a temperature and for a period of time sufficient to melt all of said materials;
(3) cooling said materials at a controlled rate of cooling.
15. A process according to claim 14 , wherein the starting materials comprise elemental starting materials.
16. A process according to claim 15 wherein 0.1≦x≦0.3, and m≦10.
17. A process according to claim 16 , wherein M is Pb, M′ is Sb, and Q is Te.
18. A method of formulating a thermoelectric material of a specific composition having the formula Ag 1−x M m M′Q 2+m , wherein
(a) M is at least one element selected from the group consisting of Pb, Sn, Ca, Sr, Ba, divalent transition metals, and combinations thereof;
(b) M′ is at least one element selected from the group consisting of Bi, Sb, and combinations thereof;
(c) Q is at least one element selected from the group consisting of Se, Te, S, and combinations thereof; and
(d) 8≦m≦24, and 0.05≦x≦0.6;
and wherein said material is made by a process comprising the steps of
(e) adding stoichiometric amounts of starting materials comprising Ag, M, M′, and Q to a reaction vessel;
(f) heating the starting materials to a temperature and for a period of time sufficient to melt all of said materials;
(g) cooling said materials at a controlled rate of cooling;
said method comprising:
(1) making a plurality of samples of said material having said composition, using said process, wherein said temperature, said period of time; and said rate of cooling are varied among the processes used to make said samples;
(2) comparing the ZT of said samples; and
(3) selecting a temperature, period of time and rate of cooling that yields a material having a desired ZT.
19. A process according to claim 18 wherein 0.1≦x≦0.3, and m≦10.
20. A process according to claim 19 , wherein M is Pb, M′ is Sb, and Q is Te.
21. An n-type semiconductor material of the formula Ag 1−x M m M′Q 2+m wherein
(a) M is at least one element selected from the group consisting of Pb, Sn, Ca, Sr, Ba, divalent transition metals, and combinations thereof;
(b) M′ is at least one element selected from the group consisting of Bi, Sb, and combinations thereof;
(c) Q is at least one element selected from the group consisting of Se, Te, S, and combinations thereof; and
(d) 8≦m≦24, and 0.01≦x<1.
22. An n-type semiconductor material according to claim 21 , wherein 0.05≦x≦0.6.
23. An n-type semiconductor material according to claim 22 , wherein M is Pb.
24. An n-type semiconductor material according to claim 22 , wherein 0.1≦x≦0.3.
25. An n-type semiconductor material according to claim 22 , wherein m is ≧10.
26. An n-type semiconductor material according to claim 22 , which is substantially free of external dopants.
27. A thermoelectric element comprising an n-type semiconductor and a p-type semiconductor joined electrically at one end to form a couple, wherein the n-type semiconductor comprises a composition having the general formula Ag 1−x M m M′Q 2+m , wherein:
(a) M is at least one element selected from the group consisting of Pb, Sn, Ca, Sr, Ba, divalent transition metals, and combinations thereof;
(b) M′ is at least one element selected from the group consisting of Bi, Sb, and combinations thereof;
(c) Q is at least one element selected from the group consisting of Se, Te, S, and combinations thereof; and
(d) 8≦m≦24, and 0.05≦x≦0.6.
28. A thermoelectric element according to claim 27 , wherein 0.1≦x≦0.3.
29. A thermoelectric element according to claim 27 , wherein M is Pb.
30. A thermoelectric element according to claim 27 , wherein Q comprises Te.
31. A thermoelectric element according to claim 27 , wherein M′ is Sb.
32. A thermoelectric element according to claim 28 , wherein m≧10.
33. A thermoelectric generator comprising a thermoelectric element according to claim 27 .
34. A method for generating electric current from heat energy, comprising applying heat energy to a thermoelectric module operating according to the Seebeck effect, wherein the thermoelectric module comprises a semiconductor material comprising a composition having the general formula Ag 1−x M m M′Q 2+m , wherein:
(a) M is at least one element selected from the group consisting of Pb, Sn, Ca, Sr, Ba, divalent transition metals, and combinations thereof;
(b) M′ is at least one element selected from the group consisting of Bi, Sb, and combinations thereof;
(c) Q is at least one element selected from the group consisting of Se, Te, S, and combinations thereof; and
(d) 8≦m≦24, and 0.01≦x<1.
35. A method according to claim 34 , wherein 0.05≦x≦0.6.
36. A method according to claim 35 , wherein 0.1≦x≦0.3.
37. A method according to claim 35 , wherein m≧10.
38. A method according to claim 35 , wherein M is Pb.
39. A method according to claim 38 , wherein M′ is Sb.
40. A method according to claim 38 , wherein Q comprises Te.
41. A method according to claim 38 , wherein the composition comprises
Ag 1−x Pb 10 M′Q 12 .
42. A method according to claim 38 , wherein the composition comprises
Ag 1−x Pb 12 M′Q 14 .
43. A method according to claim 38 , wherein the composition comprises
Ag 1−x Pb 14 M′Q 16 .
44. A method according to claim 38 , wherein the composition comprises
Ag 1−x Pb 16 M′Q 18 .
45. A method according to claim 38 , wherein, the composition comprises
Ag 1−x Pb 18 M′Q 20 .
46. A method according to claim 35 , wherein the heat energy is generated by radioactive isotope decay.
47. A method according to claim 35 , wherein the heat energy is generated by capturing solar energy.
48. A method according to claim 35 , wherein the heat energy is generated by burning fossil fuels.