Batteries: thermoelectric and photoelectric – Thermoelectric – Having particular thermoelectric composition
Reexamination Certificate
2002-04-26
2004-07-06
Ryan, Patrick (Department: 1745)
Batteries: thermoelectric and photoelectric
Thermoelectric
Having particular thermoelectric composition
C136S238000, C136S239000, C136S240000, C252S519130, C252S519140, C252S519330, C252S519400, C252S521400
Reexamination Certificate
active
06759587
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to thermoelectric materials to be employed for so-called thermoelectric conversion (i.e., direct energy conversion without use of any moving parts), including power generation on the basis of the Seebeck effect and electronic cooling on the basis of the Peltier effect. More particularly, the invention relates to thermoelectric materials comprising hybrid of organic polymer and inorganic thermoelectric materials for attaining, in combination, good moldability provided by the organic polymer and good thermoelectric characteristics provided by the inorganic thermoelectric materials. The invention also relates to a thermoelectric conversion device containing the materials and to a method for producing the materials.
2. Background Art
Thermoelectric conversion by use of a thermoelectric conversion materials; e.g., thermoelectric power generation or electronic cooling, finds utility in a simplified direct-energy-conversion apparatus having no mobile parts that generate vibration, noise, wear, etc.; having a simple, reliable structure; having a long service life; and facilitating maintenance. Thus, thermoelectric conversion is suitable for direct generation of DC power without combustion of a variety of fossil fuels or other sources and for temperature control without use of a cooling medium.
Characteristics of thermoelectric conversion materials are evaluated on the basis of thermoelectric power factor (TPF) and thermoelectric figure of merit (ZT), which are represented by the following formulas:
TPF=S
2
&sgr; [Formula 1]
ZT
=
S
2
σ
κ
′
×
T
[
Formula
2
]
wherein S represents the Seebeck coefficient; &sgr; represents electric conductivity; and &kgr; represents thermal conductivity. Thermoelectric conversion materials desirably have a high ZT; i.e., a high Seebeck coefficient (S), high electric conductivity (&sgr;), and low thermal conductivity (&kgr;).
For example, when employed for thermoelectric conversion such as thermoelectric power generation, thermoelectric conversion materials desirably have a thermoelectric figure of merit as high as ZT=0.02 or higher and to operate without variation for a long period of time under varying operation conditions. Mass production of thermoelectric power generators for use in vehicles or employing discharged heat gives rise to demand for thermoelectric conversion materials which have sufficiently high heat resistance and strength, particularly at high temperature, and resistance to deterioration in characteristics, as well as a method for producing the materials with high efficiency and at low cost.
Conventionally, PbTe or silicide materials including silicide compounds such as MSi
2
(M: Cr, Mn, Fe, or Co) and mixtures thereof have been used to serve as the aforementioned thermoelectric conversion materials.
Sb compounds such as TSb
3
(T: Co, Ir, or Ru) have also been used. For example, there has been disclosed thermoelectric materials which comprise materials containing CoSb
3
as a predominant component and an impurity added for determination of conduction type (L. D. Dudkin and N. Kh. Abriko Sov, Soviet Physics Solid State Physics (1959) p. 126; B. N. Zobrinaand, L. D. Dudkin, Soviet Physics Solid State Physics (1960) p. 1668; and K. Matsubara, T. Iyanaga, T. Tsubouchi, K. Kishimoto, and T. Koyanagi, American Institute of Physics (1995) p. 226-229).
A variety of inorganic thermoelectric materials, including Bi—(Te, Se) series (e.g., bismuth telluride); Si—Ge series; Pb—Te series; GeTe—AgSbTe series; and (Ca, Sr, Bi)Co
2
O
5
series, have been proposed and studied.
Some of the aforementioned inorganic thermoelectric materials have been proven to have excellent thermoelectric characteristics acceptable for practical use. However, these materials involve a drawback, in that they are difficult to process.
Japanese Patent Application Laid-Open (kokai) No. 8-32124 discloses a method for producing a thermoelectric conversion device including producing an ingot and cutting the ingot to thereby form a thermoelectric conversion device in the form of a rectangular prism. However, such an ingot is difficult to process, and material loss is significant. In addition, breaking and chipping during cutting is thought to lower the yield of the thermoelectric materials.
With regard to organic thermoelectric materials having good processability, polyaniline has been studied.
Another thermoelectric materials comprising polyaniline serving as organic thermoelectric materials and vanadium oxide has been proposed (E. Lazaro, M. Bhamidipati, M. Aldissi, and B. Dixon, AD Rep, p. 1-35 (1998)). Still another thermoelectric materials comprising polyaniline serving as organic thermoelectric materials and NaFeP (whiskers or nano-wires) has been proposed (J. Wang et al., 20th International Conference on Thermoelectrics, p. 352-355 (2001)).
However, these organic thermoelectric materials also involve a drawback, in that they have poor thermoelectric characteristics as compared with inorganic thermoelectric materials.
U.S. Pat. No. 5,973,050 discloses another thermoelectric materials based on organic thermoelectric materials in which metal (e.g., silver, gold, or platinum) in powder form is dispersed.
However, the organic thermoelectric materials disclosed in U.S. Pat. No. 5,973,050 has a Seebeck coefficient of p-type.
In general, thermoelectric materials employing organic thermoelectric materials exhibit p-type characteristics. When production of a thermoelectric device such as a Peltier device is contemplated, an n-type thermoelectric materials formed of the same materials as the counter p-type materials are required. Thus, provision of thermoelectric materials exhibiting the n-type thermoelectric characteristic is important.
SUMMARY OF THE INVENTION
The present inventors have conducted extensive studies in order to overcome the aforementioned drawbacks, and have found that hybridization of organic thermoelectric materials and inorganic thermoelectric materials through a specified method enables production of novel thermoelectric materials which exhibit the excellent processability of organic thermoelectric materials and the excellent thermoelectric characteristics of inorganic thermoelectric materials, and which may exhibit n-type thermoelectric characteristics. The present invention has been accomplished on the basis of this finding.
Thus, an object of the present invention is to provide thermoelectric materials having processability and excellent thermoelectric characteristics in combination and which can provide n-type thermoelectric characteristics in accordance with the nature of the employed inorganic thermoelectric materials. Another object of the invention is to provide a thermoelectric device employing the materials. Still another object of the invention is to provide a method for producing thermoelectric materials.
Accordingly, in a first aspect of the present invention, there are provided thermoelectric materials comprising an organic thermoelectric component and an inorganic thermoelectric component, wherein the organic thermoelectric component and the inorganic thermoelectric component are united in a dispersed state, the organic thermoelectric component being at least one species selected from among polyaniline and derivatives thereof; polypyrrole and derivatives thereof; polythiophene and derivatives thereof; polyphenylenevinylene derivatives; poly(p-phenylene) derivatives; polyacene derivatives; and copolymers thereof, and the inorganic thermoelectric component being at least one species selected from among Bi—(Te, Se) series, Si—Ge series, Pb—Te series, GeTe—AgSbTe series, (Co, Ir, RU)—Sb series, and (Ca, Sr, Bi)Co
2
O
5
series.
The inorganic thermoelectric component may have a particle size of several hundreds &mgr;m or less, whereby the thermoelectric materials are formed by dissolving the organic thermoelectric component in an organic solvent to thereby yield a solution; dispersing the in
Kamei Kohsuke
Tokuda Takashi
Toshima Naoki
Tsubata Akinori
Yan Hu
Hokushin Corporation
Huntley & Associates LLC.
Parsons Thomas H.
Ryan Patrick
LandOfFree
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