Methods for high figure-of-merit in nanostructured thermoelectric materials

Abstract

Thermoelectric materials with high figures of merit, ZT values, are disclosed. In many instances, such materials include nano-sized domains (e.g., nanocrystalline), which are hypothesized to help increase the ZT value of the material (e.g., by increasing phonon scattering due to interfaces at grain boundaries or grain/inclusion boundaries). The ZT value of such materials can be greater than about 1, 1.2, 1.4, 1.5, 1.8, 2 and even higher. Such materials can be manufactured from a thermoelectric starting material by generating nanoparticles therefrom, or mechanically alloyed nanoparticles from elements which can be subsequently consolidated (e.g., via direct current induced hot press) into a new bulk material. Non-limiting examples of starting materials include bismuth, lead, and/or silicon-based materials, which can be alloyed, elemental, and/or doped. Various compositions and methods relating to aspects of nanostructured theromoelectric materials (e.g., modulation doping) are further disclosed.

What is claimed is: 
     
         1 - 92 . (canceled) 
     
     
         93 . A method of forming a semiconductor alloy thermoelectric material, comprising compacting a powder by hot pressing to consolidate the powder at a pressure in a range of about 40 MPa to about 300 MPa and at a temperature in a range of about 400° C. to about 1200° C. to form the semiconductor alloy thermoelectric material comprising a plurality of randomly oriented grains having an average size below 5000 nm, wherein the semiconductor alloy thermoelectric material exhibits a ZT value between 0.8 and 4 for at least one temperature in a range of about room temperature to about 2000° C. 
     
     
         94 . The method of claim  1 , further comprising in-situ precipitating during the hot pressing one or more precipitation regions in at least some of the grains, the one or more precipitation regions having an average size of 1 nm to 50 nm. 
     
     
         95 . The method of  claim 94 , wherein the precipitation region is characterized by at least one of a different composition, a different crystalline direction and a different phase relative to the rest of the grain in which the precipitation region is formed. 
     
     
         96 . The method of claim  1 , further comprising:
 providing at least two different elemental powders; and   forming the powder by mechanically alloying the at least two different elemental powders to form a semiconductor alloy powder comprising semiconductor alloy nanoparticles.   
     
     
         97 . The method of  claim 96 , wherein:
 the step of mechanically alloying comprises milling the at least two different elemental powders; and   the semiconductor alloy nanoparticles have an average size of about 1 to about 200 nm.   
     
     
         98 . The method of claim  1 , wherein the powder comprises a mixture of at least two different elemental powders each comprising elemental nanoparticles. 
     
     
         99 . The method of claim  1 , wherein the powder comprises a semiconductor alloy powder comprising semiconductor alloy nanoparticles. 
     
     
         100 . The method of  claim 99 , wherein the powder is formed by breaking up a bulk semiconductor alloy material to form a powder comprising nanoparticles of the semiconductor alloy material. 
     
     
         101 . The method of  claim 100 , wherein the nanoparticles of the semiconductor alloy material have an average size of about 1 to 200 nm. 
     
     
         102 . The method of claim  1 , wherein the powder is consolidated at a pressure in a range of 40-160 MPa. 
     
     
         103 . The method of claim  1 , wherein the material exhibits a ZT value between 1 and 4 for at least one temperature in a range of room temperature to 2000° C. 
     
     
         104 . The method of claim  1 , wherein the material exhibits a ZT value between 1.2 and 4 for at least one temperature in a range of room temperature to 2000° C. 
     
     
         105 . The method of claim  1 , wherein the plurality of randomly oriented grains have an average size below 2000 nm. 
     
     
         106 . The method of claim  1 , wherein the plurality of randomly oriented grains have an average size below 500 nm.