Thermoelectric material system

Details Thermoelectric material system Thermoelectric material system

1999-09-09

2001-05-01

Gorgos, Kathryn (Department: 1741)

Batteries: thermoelectric and photoelectric

Thermoelectric

Having particular thermoelectric composition

C136S203000, C136S205000, C136S238000, C136S239000, C136S240000, C136S241000

Reexamination Certificate

active

06225550

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to thermoelectric devices, and more particularly to an improved thermoelectric system employing a novel magnesium antimonide semiconductor.
2. Description of the Related Art
Thermoelectric devices have been employed popularly for a many years, largely in connection with temperature regulation systems, such as heating and cooling. Thermoelectric devices of the type involved here are ordinarily solid state devices that function as heat pumps to transfer heat to or from a specific location. Fundamentally they operate under the same principles as do refrigerators or other mechanical heat pumps.
As the skilled artisan will appreciate, the viability of a material to function as a thermoelectric device depends on the efficiency of the material. See, U.S. Pat. No. 5,610,366, hereby expressly incorporated by reference. In that patent, the applicants address the dimensionless figure of merit ZT, which is related to the efficiency of the material to function as a thermoelectric device. That patent also points out how the most popularly employed materials for thermoelectric devices were developed several decades ago. Examples include those listed in that patent as well as Sb
2
Te
3
and Bi
2
Te
3
. These materials typically have exhibited a ZT of about 1, and no greater than about 1.2 (under limited operational ranges). Moreover, materials such as Bi
2
Te
3
, because of their anisotropic structure, require special processing to produce crystallographically oriented materials.
Particularly in view of technological advances requiring efficient heat transfer (e.g., for space applications, or other sensitive electronic device applications), a need has arisen for an improved material for thermoelectric device, particularly one that exhibits a ZT greater than about 0.4. Further, owing to the broad range of conditions to which the devices will be subjected, it is important for the material to yield consistent and reproducible results through a broad range of operating conditions. It is also desirable to provide a material that can be handled readily and is easy to process, so that impracticalities traditionally associated with manufacture of thermoelectric devices can be avoided.
A discussion of crystal structures for various binary intermetallic phases can be found at
Pearson's Handbook: Crystallographic Data for Intermetallic Phases, Desk Edition,
Vols. 1 and 2, P. Villars, Ed., ASM International, Materials Park (1997). Heretofore, it is believed that the only reported binary intermetallic phase of Mg
x
Sb
y
is Mg
3
Sb
2
. Mg
3
Sb
2
crystallizes in the trigonal anti-La
2
O
3
structure at room temperature and undergoes a structural transition to a high temperature beta phase that crystallizes in the body centered cubic structure of Mn
2
O
3
. Also of potential interest is K. A. Bol'shakov et al., Russian Journal of Inorganic Chemistry, Translated from Zhurnal Neorganicheskoi Khimii, 8, (12), 1418-1424 (1963).
SUMMARY OF THE INVENTION
The present invention overcomes the shortcomings of the prior art by providing an improved thermoelectric material and system. In a preferred embodiment, the material is based upon the system A
x
M
y
B
z
, where A is one or more element selected from the group consisting of Be, Mg, Ca, Sr, Ba, Al, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, Sc and mixtures thereof; B is one or more element selected from the group consisting of P, As, Sb, Bi, Ge, Sn, Pb, Si, Se, Te and mixtures thereof; and M is a transition metal, a noble metal, or a mixture thereof; and further where x ranges from about 59 to about 72, and y ranges up to about 15, and z ranges from about 25 to about 33. In one preferred embodiment, A and B adopt an anti-CaF
2
structure type. In a highly preferred embodiment, the material is Mg
x
Sb
z
further doped with another element, preferably a transition metal. Thermoelectric devices can be prepared using the material of the present invention.
The material exhibits a ZT of at least about 0.4, and is capable of exhibiting a ZT of at least about 1.2, a resistivity of at most about 30 milliohms-cm, a band gap of at least about 0.05 eV, and an estimated Seebeck coefficient in excess of about 1000 microvolts/K at room temperature. The material is generally isotropic and thus optionally does not require manufacture in a specific crystallographic orientation.


REFERENCES:
patent: 5610366 (1997-03-01), Fleurial et al.
The antimony-rich parts of the ternary systems calcium, strontium, barium and cerium with iron and antimony; structure refinements of the LaFe4Sb12-type compounds SrFe4Sr12 and CeFe4Sb12; the new compounds CaOs4Sb12 and YbOs4Sb12, Joachim W. Kaiser and W.*
Nickel-substituted Skutterudites: synthesis, structural and electrical properties, L. Chapon, D. Ravot, and J.C. Tednac, Journal of Alloys and Compounds 282 (1999) 58-63, No month/1999.*
Pearson's Handbook: Crystallographic Data for Intermetallic Phases, Desk Edition,vols. 1 and 2, P. Villars, Ed., ASM International, Materials Park (1997) (excerpt regarding Mg3Sb2), pp. 2347-2348.
Verbrugge, Dawn M.; Van Zytveld, J.B., “Electronic Properties of Liquid MgSb,” Journal of Non-Crystalline Solids, Elsevier Science Publishers B.V., p. 736-739, (1993), No month provided.
Bohmeier, H; Kunert, W.; Raschke, M.; Gotsch, A., “Kontaktwerkstoffe fur Vakuumleistungsschalter auf NE-Metall-Basis,” Electrie 31, vol. 31 (No. 9), p. 490-491, (1997), No month provided.
Merlo, F; Pani, M.; Fornasini, M.L., “RMX Compounds Formed by Alkaline Earths Europium and Ytterbium-I. Ternary Phases with M=Cu, Ag, Au X=Sb,Bi,” Journal of Less Common Metals, vol. 166 (No. 2), p. 1990-1911, (Nov., 1990).
Verbrugge D. M. et al., “Liquid Semiconductor and Thermoelectric Power Generation: MG-SB,” Journal of Physics D. Applied Physics, IOP Publishing (Bristol, GB), vol. 26 (No. 10), p. 1722-1726, (Mar. 1993).
Kajikawa T. et al., “Thermoelectric Properties Control Due to Doping Level and Sinteringconditions for FGM Thermoelectric Element,” Materials Science, Forum, vols. 308-311 (Aedermannsfdorf, CH), p. 687-692, (1999), No month provided.
K.A. Bol'Shakov et al., ‘Russian Journal of Inorganic Chemistry, Translated from Zhurnal Neorgranicheskoi Khimii,’ vol. 8 (No. 12), p. 1418-1421, (1963), No month available.

Affiliated with

Also associated with

Rating

Thermoelectric material system does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Thermoelectric material system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermoelectric material system will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2566580