Thermoelectric skutterudite compositions and methods for producing the same
Compositions related to skutterudite-based thermoelectric materials are disclosed. Such compositions can result in materials that have enhanced ZT values relative to one or more bulk materials from which the compositions are derived. Thermoelectric materials such as n-type and p-type skutterudites with high thermoelectric figures-of-merit can include materials with filler atoms and/or materials formed by compacting particles (e.g., nanoparticles) into a material with a plurality of grains each having a portion having a skutterudite-based structure. Methods of forming thermoelectric skutterudites, which can include the use of hot press processes to consolidate particles, are also disclosed. The particles to be consolidated can be derived from (e.g., grinded from), skutterudite-based bulk materials, elemental materials, other non-Skutterudite-based materials, or combinations of such materials.
1. A method of fabricating an enhanced thermoelectric material comprising:
providing at least one starting material which comprises at least one skutterudite-based starting material;
generating a plurality of nanoparticles having an average particle size less than about 500 nm from the at least one skutterudite-based starting material; and
consolidating the nanoparticles under pressure in a range from about 10 MPa to about 300 MPa at an elevated temperature to form a densified material, the densified material comprising a plurality of grains, each of the plurality of grains exhibiting a skutterudite-based structure, and the densified material exhibits a ZT value greater than about 0.8,
wherein the densified material exhibits a higher ZT value at least at one temperature relative to at least one of the skutterudite-based starting materials.
2. The method of claim 1 , wherein the at least one starting material comprises at least one element of the skutterudite-based structure of each of the plurality of grains.
3. The method of claim 2 , wherein the at least one starting material comprises filler atoms in the skutterudite-based structure.
4. The method of claim 2 , wherein the skutterudite-based structure lacks filler atoms.
5. The method of claim 1 , wherein the at least one skutterudite-based starting material comprises at least two different skutterudite-based starting materials.
6. The method of claim 5 , wherein the step of generating comprises grinding the at least two different skutterudite-based starting materials separately or simultaneously.
7. The method of claim 1 , wherein the step of generating the plurality of nanoparticles includes grinding the at least one starting material.
8. The method of claim 7 , further comprising:
cooling the at least one starting material while performing the step of grinding.
9. The method of claim 7 , wherein the step of grinding the at least one starting material comprises utilizing ball milling.
10. The method of claim 1 , wherein the step of consolidating the nanoparticles includes using a hot press process.
11. The method of claim 10 , wherein the step of using a hot press process including using at least one of direct current induced hot press, unidirectional hot press, plasma pressure compaction, and isostatic hot press.
12. The method of claim 1 , further comprising:
selecting the pressure to be in a range from about 10 MPa to about 100 MPa.
13. The method of claim 1 , further comprising:
selecting the elevated temperature to be in a range from about 200° C. to about 800° C.
14. The method of claim 1 , further comprising maintaining the nanoparticles at the elevated temperature for a time period between about 1 sec and about 10 hours.
15. The method of claim 1 , wherein the plurality of nanoparticles exhibit an average particle size smaller than about 50 nm.
16. The method of claim 1 , wherein the plurality of grains in the densified material exhibit an average grain size smaller than about 5 μm.
17. The method of claim 1 , wherein the skutterudite-based structure comprises a crystal having metal atoms forming a cubic sublattice.
18. The method of claim 17 , wherein the metal atoms comprise at least two of cobalt, iron, nickel, rhodium, iridium, ruthenium, and osmium.
19. The method of claim 1 , wherein the skutterudite-based structure comprises a filler-containing skutterudite material.
20. The method of claim 1 , wherein the densified material exhibits the higher ZT value at a temperature below about 800° C.
21. The method of claim 1 , wherein an average grain size of the densified material is larger than an average size of the nanoparticles.