JP2010040724A - Thermoelectric conversion material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide materials which have a high Seebeck coefficient in a temperature range below room temperature. <P>SOLUTION: Disclosed is the thermoelectric conversion materials containing rutile type titanium oxide doped with boron. Especially, the rutile type titanium oxide doped with the boron has a Seebeck coefficient of ≥500 μV/K in a temperature range below 300 K. Those thermoelectric conversion element materials are doped with powder of titanium and boron oxide through plasma sintering. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thermoelectric conversion material, and particularly to a thermoelectric conversion material having a remarkably high Seebeck coefficient in a low temperature region.

  In recent years, research on thermoelectric conversion has been attracting attention due to the growing environmental awareness, and research that collects or reuses heat that has been overlooked as waste heat has attracted attention. Specifically, for example, a method of recovering heat generated by an industrial compressor or resistor as electricity or use as a power source for an artificial satellite can be mentioned.

BiTe-based materials are well known as thermoelectric conversion materials, and PbTe-based and SiGe-based materials are also known. One of the evaluations of thermoelectric conversion materials is the Seebeck coefficient, and a high value plays an important role in thermoelectric conversion. The thermoelectric conversion material utilizes characteristics mainly from room temperature (300K) to 500K, and about 1000K in the case of SiGe series. In fact, Bi ₂ Te ₃ has high thermoelectric performance near room temperature.

JP 2006-176360 A JP-A-11-279605

  However, the conventional technique has the following problems. First, since conventional thermoelectric conversion materials (thermoelectric conversion element materials) such as BiTe use heavy metals or rare metals, there are concerns about environmental impacts, and there are essential problems such as material depletion. It has been demanded.

Further, conventional thermoelectric conversion materials are assumed to be used in a high temperature range, and there are few materials in an environment below room temperature. In fact, Bi ₂ Te ₃ rapidly decays the Seebeck coefficient below room temperature, and is not a useful thermoelectric material below 200K. The Seebeck coefficient of the BiSb alloy is a high value at 70K to 120K, but the performance deteriorates at a temperature higher than that. That is, for example, a material showing a high Seebeck coefficient in a wide temperature range of 100K to 300K has not been known.

  This invention is made | formed in view of the above, Comprising: It aims at providing the material which has a high Seebeck coefficient in the temperature range lower than room temperature. It is another object of the present invention to provide a thermoelectric conversion material that can be used in a temperature range lower than room temperature.

  In order to achieve the above object, the invention according to claim 1 is a thermoelectric conversion material containing rutile titanium oxide doped with boron (B).

  The invention according to claim 2 is the thermoelectric conversion material according to claim 1, wherein the Seebeck coefficient in a temperature range of 300 K or less is 500 μV / K or more.

  The doping method is not particularly limited, and examples thereof include a plasma sintering method, a vapor deposition method, and a sputtering method.

  According to the present invention, an effective thermoelectric conversion material in a low temperature range can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The rutile titanium oxide doped with boron can be obtained by a discharge plasma sintering method. Specifically, a raw material powder obtained by adding B ₂ O ₃ powder to TiO ₂ was heated and sintered at 1200 ° C. in a vacuum degree of 5 Pa to obtain a pellet-shaped sintered body having a diameter of 10 mm. Although illustration is omitted, when the crystal structure of the obtained sintered body was measured by X-ray diffraction, it was confirmed to be a rutile type. It was also confirmed that there was conductivity at room temperature.

Boron doping was also performed by vacuum deposition using a single crystal TiO ₂ substrate. Specifically, boron was vapor-deposited at 900 ° on a TiO ₂ single crystal substrate and doped by thermal diffusion. The dope amount can be variously adjusted, but can be 5 × 10 ¹⁸ cm ^{−3 to} 5 × 10 ¹⁹ cm ⁻³ . In addition, although illustration is abbreviate | omitted similarly, when the crystal structure of the obtained sintered compact was measured by X-ray diffraction, it confirmed that it was a rutile type. It was also confirmed that there was conductivity at room temperature.

FIG. 1 shows the results of measuring the Seebeck coefficient of a boron-doped rutile TiO ₂ of a plasma sintered body and a single crystal body. In the figure, the Seebeck coefficients of BiSb-based materials and BiTeSe-based materials known as thermoelectric conversion materials are plotted together. As is apparent from the figure, in the case of a single crystal, the value is 800 μV / K in a temperature range of 100 K, and even a sintered body shows an extremely high value of 500 μV / K or more in an atmosphere of 300 K or less. . Note that the sintered body is obtained by doping boron percentage during weighing as _{TiO 2 -5mol% B 2 O 3} , the single crystal is doped amount of boron is ^5x10 18 ^{cm -3.}

  The measurement results of the Seebeck coefficient indicate that the product of the present invention can be developed as an element capable of exhibiting stable performance in a wide temperature range such as 100K to 300K.

  According to the present invention, effective use of low-temperature waste heat and Peltier cooling for special applications are possible.

It is the figure which measured the temperature dependence of Seebeck coefficient.

Claims (2)

  A thermoelectric conversion material containing rutile titanium oxide doped with boron. The thermoelectric conversion material according to claim 1, wherein the Seebeck coefficient in a temperature range of 300K or less is 500 µV / K or more.