Synthesis of silver, antimony, and tin doped bismuth telluride nanoparticles and bulk bismuth telluride to form bismuth telluride composites

1. A thermoelectric material comprising bismuth telluride nanoparticles, the nanoparticles being dispersed in a matrix material that comprises particulate bismuth telluride, wherein:

the thermoelectric material comprises a homogenized thermoelectric material having a thermoelectric figure of merit (ZT) of at least 1 or more; and

the bismuth telluride nanoparticles are doped with at least one or more of silver, antimony, tin, and/or a combination thereof;

the bismuth telluride nanoparticles have a maximum dimension less than 200 nanometers; and

the bismuth telluride nanoparticles are present in the thermoelectric material in an amount ranging from more than 20% to about 30% by weight, based on the total weight of the thermoelectric material; and

the particulate bismuth telluride is present in the thermoelectric material in an amount ranging from 70% to less than 80% by weight, based on the total weight of the thermoelectric material.

2. The thermoelectric material according to claim 1 , wherein the bismuth telluride nanoparticles are doped with silver.

3. The thermoelectric material according to claim 1 , wherein the bismuth telluride nanoparticles include one or more of:

p-type doped bismuth telluride nanoparticles comprising Bi 2-x Sb x Te 3 ;

p-type doped bismuth telluride nanoparticles comprising Bi 2-x Sn x Te 3 ;

p-type doped bismuth telluride nanoparticles comprising Bi 2-x Ag x Te 3 with Ag in lattice sites; and

n-type doped bismuth telluride nanoparticles comprising Bi 2-x Ag x Te 3 with Ag in interstitial sites.

4. The thermoelectric material of claim 1 , wherein:

the thermoelectric material is a metallic doped thermoelectric nanocomposite material in the form of a pellet, a powder, or a dispersion and has a dopant concentration between 4% to 10% and ratio of dopant to bismuth from 1:4 to 1:11;

the bismuth telluride nanoparticles are present in the thermoelectric material in an amount of 30% by weight, based on the total weight of the thermoelectric material; and

the particulate bismuth telluride is present in the thermoelectric material in an amount ranging of 70% by weight, based on the total weight of the thermoelectric material.

5. An apparatus comprising the thermoelectric material of claim 1

wherein the bismuth telluride nanoparticles contain 35 to 49 by atomic percent of bismuth, and 40 to 65 by atomic percent of tellurium, or the bismuth telluride nanoparticles have an atomic weight percent ratio of bismuth to tellurium that ranges from 0.43:1 to 1:1; and

wherein the apparatus is selected from the group consisting of a light-emitting diode, a laser, an optical detector, an infrared detector, a field-effect detector, a static electric field detector, a resonant tunneling diode, a photonic bandgap structure, an optical waveguide, an optical coupler, and a chemical sensor.

6. A thermoelectric device comprising:

a first electrical connector and a second electrical connector; and

the thermoelectric material of claim 1 , the thermoelectric material in electrical contact with the first electrical connector and the second electrical connector.

7. The thermoelectric device of claim 6 , wherein the bismuth telluride nanoparticles include one or more of:

p-type doped bismuth telluride nanoparticles comprising Bi 2-x Sb x Te 3 ;

p-type doped bismuth telluride nanoparticles comprising Bi 2-x Sn x Te 3 ;

p-type doped bismuth telluride nanoparticles comprising Bi 2-x Ag x Te 3 with Ag in lattice sites; and

n-type doped bismuth telluride nanoparticles comprising Bi 2-x Ag x Te 3 with Ag in interstitial sites.

8. A method for making the thermoelectric material of claim 1 , the method comprising synthesizing the bismuth telluride nanoparticles, the synthesizing comprising:

mixing a bismuth salt with a long-chain alkane hydrocarbon forming a bismuth salt solution;

reacting the bismuth salt solution with a long-chain fatty amine forming a bismuth ion solution;

adding tellurium to a tertiary alkylphosphine, thereby forming a telluride salt solution;

adding a surfactant to the bismuth ion solution; and

mixing the surfactant containing bismuth ion solution with the telluride salt solution forming a nanoparticle dispersion containing bismuth telluride nanoparticles.

9. The method of claim 8 , wherein the method is a solvothermal method for synthesizing bismuth telluride nanoparticles.

10. The method of claim 8 , further comprising isolating bismuth telluride nanoparticles from the nanoparticle dispersion, wherein isolating includes:

adding a biphasic solvent to the nanoparticle dispersion;

centrifuging the nanoparticle dispersion that includes the biphasic solvent; and

removing sedimented bismuth telluride nanoparticles from the centrifuged nanoparticle dispersion.

11. The method of claim 8 , wherein:

each method step is followed by at least one of incubation and refluxing for at least about 10 minutes at a temperature ranging from about 150° C. to about 170° C.; and/or

the long-chain fatty amine comprises oleylamine; and/or

the tertiary alkylphosphine comprises trioctyl phosphine; and/or

the surfactant comprises oleic acid.

12. A metallic doped thermoelectric nanocomposite material comprising the thermoelectric material of claim 1 , wherein the bismuth telluride nanoparticles are doped with at least one or more of silver, antimony, tin, and/or a combination thereof such that the dopant concentration may be between 4% to 10% and ratio of dopant to bismuth may be from 1:4 to 1:11.

13. A method for making the thermoelectric material of claim 1 , the method comprising synthesizing the doped bismuth telluride nanoparticles, the synthesizing comprising:

mixing a bismuth salt with a long-chain alkane hydrocarbon forming a bismuth salt solution;

dispersing the bismuth salt solution and a metal salt in a long-chain fatty amine thereby forming a doped bismuth salt solution, the metal salt including at least one or more of a silver salt, an antimony salt, a tin salt, and/or a combination thereof;

adding tellurium to a tertiary alkylphosphine, thereby forming a telluride salt solution;

adding a surfactant to the doped bismuth salt solution; and

mixing the surfactant containing doped bismuth salt solution with the telluride salt solution forming a nanoparticle dispersion containing doped bismuth telluride nanoparticles.

14. The method of claim 13 , wherein the method is a solvothermal method for synthesizing doped bismuth telluride nanoparticles.

15. The method of claim 13 , further comprising isolating doped bismuth telluride nanoparticles from the nanoparticle dispersion, wherein isolating includes:

adding a biphasic solvent to the nanoparticle dispersion;

centrifuging the nanoparticle dispersion containing the biphasic solvent; and

removing sedimented doped bismuth telluride nanoparticles from the centrifuged nanoparticle dispersion.

16. The method of claim 13 , wherein:

each method step is followed by at least one of incubation and refluxing for at least about 10 minutes at a temperature ranging from about 150° C. to about 170° C.; and/or

the long-chain fatty amine comprises oleylamine; and/or

the tertiary alkylphosphine comprises trioctyl phosphine; and/or

the surfactant comprises oleic acid.

17. A method for making the thermoelectric material of claim 1 , the method comprising forming the particulate bismuth telluride, the forming comprising:

dissolving a bismuth precursor in an acid to form a bismuth salt solution;

mixing telluric acid dissolved in an organic diol with the bismuth salt solution, thereby forming a reaction mixture;

reacting a basic amine with the reaction mixture; and

precipitating the particulate bismuth telluride from the reaction mixture with a reducing agent.

18. A method for forming the thermoelectric material of claim 1 , the method comprising:

treating bismuth telluride nanoparticles with a hydrazine solution;

mixing particulate bismuth telluride with the treated bismuth telluride nanoparticles in an aqueous solution thereby forming a thermoelectric material precursor;

stirring the thermoelectric material precursor for 2-3 hours to form a homogenized thermoelectric material;

centrifuging the homogenized thermoelectric material forming a powder composite material; and

pressing the powder composite material to form the thermoelectric material.

19. The method of claim 18 , wherein:

the bismuth telluride nanoparticles are doped with at least one or more of silver, antimony, tin, and/or a combination thereof, or the bismuth telluride nanoparticles are non-doped bismuth telluride nanoparticles; and/or

pressing the powder composite material includes using a carver press.