Systems and methods of fabrication and use of NbFeSb P-type half-heusler thermoelectric materials
Discussed herein are half-Heusler thermoelectric materials including niobium, iron, antimony, and titanium that are formed by ball-milling and hot-pressing the ball-milled power to obtain various thermoelectric properties and an average grain size above 1 μm.
1. A method of fabricating a thermoelectric component, comprising:
forming an ingot comprising niobium, iron, antimony, and titanium according to a formula Nb 1-x Ti x FeSb;
ball-milling the ingot to form a ball-milled powder;
hot-pressing the ball-milled powder between 1100 K and 1400 K to form a thermoelectric component comprising a power factor above about 60 μW cm −1 K −2 from about 300K to about 775K and comprising a plurality of grains of an average grain size above 1.0 μm.
2. The method of claim 1 , wherein x is from about 0.02 to about 0.7.
3. The method of claim 1 , further comprising: subsequent to forming the ingot, melting the ingot at least once and reforming the ingot to enhance a uniformity of the ingot.
4. The method of claim 1 , further comprising ball-milling the ingot from 10 minutes to 70 hours.
5. The method of claim 1 , further comprising hot-pressing the ball-milled powder to form a plurality of grains of an average grain size from about 0.25 μm to about 14 μm.
6. The method of claim 1 , further comprising hot-pressing the ball-milled powder to form the thermoelectric component with a ZT above 0.6 above about 650 K.
7. The method of claim 1 , wherein ball-milling comprises more than one cycle.
8. A thermoelectric device comprising:
a hot-pressed component of ball-milled powder according to a formula Nb 1-x Ti x FeSb, wherein the component comprises a power factor above about 60 μW cm −1 K −2 from about 300 K to about 775 K and an average grain size above 1 μm.
9. The device of claim 8 , wherein x is from 0.02-0.7.
10. The device of claim 8 , wherein the power factor of the component is above about 80 μW cm −1 K −2 from about 300 K to about 500 K.
11. The device of claim 8 , further comprising an output power density (ω) of at least 10 Wcm −2 above about 600 K.
12. The device of claim 8 , further comprising a lattice thermal conductivity (κ L ) less than 8 Wm −1 K −1 above about 500 K.
13. The device of claim 8 , further comprising a plurality of grains of an average grain size from about 2.5 μm to about 4.50 μm.
14. A thermoelectric device comprising:
a hot-pressed component of ball-milled powder according to a formula Nb 1-x Ti x FeSb, wherein the hot-pressed component comprises a plurality of grains of an average grain size above 1.0 μm, a ZT above 0.6 above about 650 K, and wherein x is from 0.02 to 0.7.
15. The device of claim 14 , wherein the hot-pressed component comprises a total thermal conductivity (κ tot ) of less than about 10 W m −1 K −1 from about 425 K to about 1000 K.
16. The device of claim 15 , wherein the hot-pressed component comprises a total thermal conductivity (κ tot ) of less than about 10.5 Wm −1 K −1 from about 480K to about 1000K.
17. The device of claim 14 , wherein a Hall mobility (μ H ) of the hot-pressed component is above 16 cm 2 V s −2 from about 300K to about 450K.
18. The device of claim 14 , wherein x is from 0.1 to 0.5.
19. The thermoelectric device of claim 14 , wherein the hot-pressed component comprises a power factor above about 60 μW cm −1 K −2 from about 300K to about 775K.
20. The device of claim 14 , further comprising a plurality of grains of an average grain size from about 2.5 μm to about 4.50 μm.