JPH0878733A - Cusns group thermoeletric conversion semiconductor material and its manufacturing method - Google Patents

Abstract

PURPOSE: To obtain a thermoelectric material both high in a thermoelectromotive force and electric conductivity and excellent in thermoelectric conversion performance by a method wherein materials are mixed and sintered so that an atomic ratio of Cu, Sn and S is set to be a specific ratio to form a CuSnS alloy, consequently a metal Cu and Cu4 SnS4 being contained in the alloy. CONSTITUTION: Materials are weighed and mixed so that an atomic ratio of Cu, Sn and S is 7 to 9:1:3.5 to 4.5. These materials are heated and melted in a vacuous sealing state to obtain an ingot. Next, the obtained ingot is pulverized by a ball mill to be a thermoelectric conversion semiconductor powder comprising a CuSnS alloy. Further, the thermoelectric conversion semiconductor powder is placed in a metal mold and heated for 20min. at pressure of Iton/cm<2> , and the obtained molded body is heated at a temperature of 973K in a vacuous furnace and held for three hours and sintered. As a result, Cu4 SnS4 in a CuSnS alloy and a metal Cu high in electric conductivity exist together, and the electric conductivity and thermoelectric performance index as the entire alloy are enhanced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel CuSnS-based thermoelectric conversion semiconductor material used in a thermoelectric generator and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, CuSnS alloy is known as one of the materials exhibiting the properties of thermoelectric conversion semiconductors used for thermoelectric power generation.

[0003]

Conventionally known Cu
The thermoelectric conversion semiconductor mainly composed of SnS alloy is Cu_FourSnS
_FourAlthough it has a composition, its thermoelectric performance is still sufficient.
Instead, it has not been put to practical use. The present invention
The purpose of solving the problem of the prior art is
CuSnS alloy-based thermoelectric conversion semiconductor having electrical performance and the same
It is to provide a manufacturing method of.

[0004]

The present invention provides (1) CuSn
A thermoelectric conversion semiconductor material made of an S alloy, wherein CuSnS-based thermoelectric conversion semiconductor material containing Cu and Cu ₄ SnS ₄ therein, and (2) C
The atomic ratio of u, Sn and S is 7-9: 1: 3.5-
Material of Cu in proportions such that 4.5, were mixed Sn and S, and sintered after melted by heating under reduced pressure to an CuSnS alloy, metallic Cu and Cu ₄ SnS the該合in gold at that time
It is a method for producing a CuSnS-based thermoelectric conversion semiconductor material, characterized in that it contains ₄ .

CuSnS-based thermoelectric conversion semiconductor material of the present invention
Is the conventionally known Cu_FourSnS _FourCu increased from composition
And coexist with metallic Cu having high electric conductivity in the crystal.
In order to improve the electrical conductivity of the alloy as a whole,
This is intended to improve the electric performance index. Money like this
Genus Cu and Cu_FourSnS_FourCuSnS alloy containing
Then, the ratio of Cu, Sn and S in the alloy is 7 in atomic ratio.
~ 9: 1: 3.5-4.5 CuSnS alloy
It

The thermoelectric conversion semiconductor material of the present invention contains, for example, copper (Cu), tin (Sn) and sulfur (S) in an atomic ratio of 7 to 7.
It can be manufactured by mixing so as to be 9: 1: 3.5 to 4.5, heating and melting under reduced pressure, and then sintering. Here, if the atomic ratio of Cu to Sn is less than 7 or more than 9, it becomes difficult to obtain a CuSnS alloy in which metal Cu and Cu ₄ SnS ₄ coexist.

[0007]

The performance of the thermoelectric conversion semiconductor can be evaluated by the thermoelectric performance index Z represented by the following equation.

[Formula 1] Z = α ² · σ / κ In the formula, α is a thermoelectromotive force, σ is an electrical conductivity, and κ is a thermal conductivity. This formula shows that the thermoelectric performance of the thermoelectric conversion semiconductor can be improved by increasing the thermoelectromotive force or the electric conductivity or decreasing the thermal conductivity. In the CuSnS-based thermoelectric conversion semiconductor material of the present invention, CuSn
By increasing the ratio of Cu in the S alloy so that Cu ₄ SnS ₄ exhibiting semiconductor characteristics and metal Cu having high electric conductivity coexist in the material, the electric conductivity of the alloy as a whole is improved. It is intended to improve the thermoelectric figure of merit shown.

[0008]

EXAMPLES The effects of the present invention will be described more specifically with reference to the following examples. (Example 1, Comparative Examples 1 to 6) First, copper (Cu) and tin (S
n) and sulfur (S) were weighed and mixed so as to have the atomic ratios shown in Table 1 to obtain raw materials. This raw material was heated and melted in a vacuum sealed state to obtain an ingot. Then, the obtained ingot was crushed by a ball mill to obtain a thermoelectric conversion semiconductor powder made of CuSnS alloy. Furthermore, putting each thermoelectric conversion semiconductor powder in a mold, 2 at a pressure of 1 ton / cm ²
The molded body was obtained by heating for 0 minutes. 9 this molded body in a vacuum furnace
It was heated to a temperature of 73 K and held for 3 hours for sintering. These operating procedures are shown in FIG.

[0009]

[Table 1]

The thermoelectric figure of merit Z (K ^-1 ) at 293K was determined for the sample of Example 1 and the sample of the highest performance Cu ₄ SnS ₄ composition of the comparative examples. The results are shown in Table 2, and it can be seen that the thermoelectric conversion semiconductor obtained in Example 1 is superior in thermoelectric performance to the conventional thermoelectric conversion semiconductor having the Cu ₄ SnS ₄ composition.

[0011]

[Table 2]

The X-ray diffraction measurement results of the samples obtained in Example 1 and Comparative Examples 1 to 6 are shown in FIGS. Figure 2
From FIG. 8, both metal Cu and Cu ₄ SnS ₄ are present in the thermoelectric conversion semiconductor of the Cu ₈ SnS ₄ composition of Example 1, but one of them is present in the thermoelectric conversion semiconductors of Comparative Examples 1 to 6. It can be seen that only the metal Cu and Cu ₄ SnS ₄ are not present at the same time because they are only detected.

FIG. 9 shows the relationship between the thermoelectromotive force (α) and the temperature measured for the samples of Example 1 and Comparative Examples 1 to 6.
0 shows the relationship between the electric conductivity (σ) measured for the samples of Example 1 and Comparative Examples 1 to 4 and the temperature. FIG. 11 shows the relationship between α ² · σ obtained from these values and the reciprocal of temperature.
Shown in 9 to 11, the thermoelectric conversion semiconductor of Example 1 has higher thermoelectromotive force and electric conductivity and a larger value of α ² · σ than those of Comparative Example. Therefore, the thermoelectric figure of merit represented by the above formula is obtained. It can be seen that the value of Z is also large and that it has high thermoelectric performance.

[0014]

The thermoelectric conversion semiconductor material made of the CuSnS alloy of the present invention has high thermoelectromotive force and high electric conductivity,
It is a thermoelectric material with excellent thermoelectric conversion performance. Further, according to the method of the present invention, the thermoelectric conversion semiconductor material having the above-mentioned excellent properties can be easily produced.

[Brief description of drawings]

FIG. 1 is a flow diagram illustrating an operation procedure in an example and a comparative example.

FIG. 2 is an X-ray diffraction chart for the sample obtained in Example 1.

FIG. 3 is an X-ray diffraction chart for the sample obtained in Comparative Example 1.

FIG. 4 is an X-ray diffraction chart of the sample obtained in Comparative Example 2.

5 is an X-ray diffraction chart for the sample obtained in Comparative Example 3. FIG.

FIG. 6 is an X-ray diffraction chart for the sample obtained in Comparative Example 4.

7 is an X-ray diffraction chart for the sample obtained in Comparative Example 5. FIG.

FIG. 8 is an X-ray diffraction chart for the sample obtained in Comparative Example 6.

FIG. 9 is a graph showing the relationship between thermoelectromotive force and temperature for the samples obtained in Examples and Comparative Examples.

FIG. 10 is a graph showing the relationship between electrical conductivity and temperature for the samples obtained in Examples and Comparative Examples.

FIG. 11 shows α ^{2 of} samples obtained in Examples and Comparative Examples.
A graph showing the relationship between the value of σ and the reciprocal of temperature.

Claims (2)

[Claims] 1. A thermoelectric conversion semiconductor material made of a CuSnS alloy, wherein Cu and Cu ₄ SnS _{4 are} contained in the material.
A CuSnS-based thermoelectric conversion semiconductor material containing: 2. The ratio of Cu, Sn and S is 7 to 10 in atomic ratio.
C of the raw material in a ratio of 9: 1: 3.5 to 4.5
u, Sn and S are mixed, heated and melted under reduced pressure and then sintered to form a CuSnS alloy, in which case the metal C is contained in the alloy.
A method for producing a CuSnS-based thermoelectric conversion semiconductor material, characterized by containing u and Cu ₄ SnS ₄ .