Compound semiconductor and use thereof

Abstract

The present invention provides a novel compound semiconductor that has improved thermoelectric figure of merit as well as excellent electric conductivity, and thus, can be applied for various uses such as thermoelectric conversion material of a thermoelectric conversion device, a solar battery, and the like, and a method for preparing the same.

Claims

1. A compound semiconductor represented by the following Chemical Formula 1:
Pr.sub.xS.sub.yCo.sub.4Sb.sub.12-zQ.sub.z  Chemical Formula 1 In the Chemical Formula 1, Q includes at least one of O, Se and Te, x, y, and z means the mole ratio of each element, wherein 0<x<1, 0<y<1, and 0<z<12.

2. The compound semiconductor according to claim 1, wherein in the Chemical Formula 1, x and y fulfill x/y<1.

3. The compound semiconductor according to claim 1, wherein in the Chemical Formula 1, x and y fulfill 0<x+y≤1.

4. The compound semiconductor according to claim 1, wherein in the Chemical Formula 1, the mole ratio of x to 1 mole of z is 0.01 to 0.5 moles.

5. The compound semiconductor according to claim 1, wherein in the Chemical Formula 1, 0.01≤x<0.2, 0.1≤y≤0.5, and 0.01≤z≤1.

6. The compound semiconductor according to claim 1, wherein in the Chemical Formula 1, Q is Te.

7. A method for preparing a compound semiconductor of claim 1, comprising the steps of: mixing Pr, S, Co, Sb, and the element Q (Q includes at least one of O, Se and Te) in the contents fulfilling the compound composition of the following Chemical Formula 1, to prepare a mixture; and heat treating the mixture:
Pr.sub.xS.sub.yCo.sub.4Sb.sub.12-zQ.sub.z  Chemical Formula 1 in the Chemical Formula 1, Q includes at least one of O, Se and Te, x, y, and z means the mole ratio of each element, wherein 0<x<1, 0<y<1, and 0<z<12.

8. The method according to claim 7, wherein the heat treatment step is conducted at 400° C. to 800° C.

9. The method according to claim 7, further comprising a step of cooling, after the heat treatment step.

10. The method according to claim 7, further comprising a step of pressurized sintering, after the heat treatment step.

11. A thermoelectric conversion device comprising the compound semiconductor according to claim 1.

12. A solar battery comprising the compound semiconductor according to claim 1.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a graph showing the evaluation results of lattice thermal conductivity(k.sub.L) of the compound semiconductors of Examples 1 to 4 (Ex. 1 to Ex. 4) and Comparative Example 1 to 3(Comp. Ex. 1 to Comp. Ex. 3).

(2) FIG. 2 is a graph showing the evaluation results of thermoelectric figure of merit(ZT) of the thermoelectric devices comprising the compound semiconductors of Examples 1 to 4 (Ex. 1 to Ex. 4) and Comparative Examples 1 to 3(Comp. Ex. 1 to Comp. Ex. 3).

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) The present invention will be explained in more detail in the following examples. However, these examples are presented only as the illustrations of the present invention, and the scope of the present invention is not limited thereby.

Example 1

(4) In order to synthesize Pr.sub.0.025S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6, powder type Pr, S, Co, Sb and Te were weighed, and then, were put in an alumina mortar and mixed. The mixed materials were put in a carbide mold to make a pellet, and put in a fused silica tube and vacuum sealed. And, it was put in a box furnace and heated at 680° C. for 15 hours to obtain Pr.sub.0.025S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6. Thereafter, it was gradually cooled to room temperature, and filled in a graphite mold for spark plasma sintering, and then, spark plasma sintering was conducted at a temperature of 650° C. and a pressure of 50 MPa for 10 minutes. The relative density of the obtained compound semiconductor was measured to be 98% or more.

Example 2

(5) A compound semiconductor was prepared by the same method as Example 1, except that the composition of the mixture was changed to Pr.sub.0.05S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

Example 3

(6) A compound semiconductor was prepared by the same method as Example 1, except that the composition of the mixture was changed to Pr.sub.0.075S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

Example 4

(7) A compound semiconductor was prepared by the same method as Example 1, except that the composition of the mixture was changed to Pr.sub.0.1S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

Comparative Example 1

(8) A compound semiconductor was prepared by the same method as Example 1, except that Co, Sb and Te were prepared as reagents, and the composition of the mixture was changed to Co.sub.4Sb.sub.11.4Te.sub.0.6.

Comparative Example 2

(9) A compound semiconductor was prepared by the same method as Example 1, except that Pr, Co, Sb and Te were prepared as reagents, and the composition of the mixture was changed to Pr.sub.0.05Co.sub.4Sb.sub.11.4Te.sub.0.6.

Comparative Example 3

(10) A compound semiconductor was prepared by the same method as Example 1, except that S, Co, Sb and Te were prepared as reagents, and the composition of the mixture was changed to S.sub.0.2Co.sub.4Sb.sub.11.4Te.sub.0.6.

Experimental Example 1: Measurement of Lattice Thermal Conductivity

(11) The lattice thermal conductivities of the compound semiconductors obtained in Examples and Comparative Examples were measured, and the results were shown in FIG. 1.

(12) Specifically, the compound semiconductors obtained in Examples and Comparative Examples were processed into coin-type of a diameter of 12.7 mm and a height of 1.5 mm to manufacture specimens. And, for the specimen, thermal conductivity was calculated from the measurement values of thermal diffusivity according to a laser flash method (Netzsch, LFA-457) in the range of 50° C. to 500° C., specific heat, and density, and then, a Lorenz number was calculated and the value was applied for the calculated thermal conductivity to obtain lattice thermal conductivity(k.sub.L), and the results were shown in the following Table 1 and FIG. 1.

(13) TABLE-US-00001 TABLE 1 Temper- Lattice thermal conductivity(W/mK) ature Example Comparative Example (°C.) 1 2 3 4 1 2 3 50 1.98 1.97 1.98 2.00 3.33 3.58 2.19 100 1.84 1.84 1.85 1.87 3.07 3.29 2.04 200 1.62 1.63 1.63 1.66 2.65 2.80 1.80 300 1.46 1.47 1.47 1.50 2.32 2.44 1.62 400 1.36 1.37 1.36 1.39 2.09 2.18 1.51 500 1.30 1.31 1.30 1.32 1.93 2.03 1.44

(14) As the results of experiments, Examples 1 to 4 exhibited remarkably decreased lattice thermal conductivity over the whole temperature measurement sections, compared to Comparative Example 1 without filler, Comparative Example 2 wherein Pr was filled alone, and Comparative Example 3 wherein S was filled alone. Such results are due to the decrease in lattice thermal conductivity, as chalcogen element Q is substituted at the Sb position, and Pr and S are filled in an optimum content into Co—Sb based n-type skutterudite.

Experimental Example 2: Thermoelectric Figure of Merit(ZT)

(15) The thermoelectric figures of merit of the compound semiconductors obtained in Examples and Comparative Examples were measured, and the results were shown in the following Table 2 and FIG. 2.

(16) The compound semiconductors obtained in Examples and Comparative Examples were processed into rectangular-type with width 3 mm, length 3 mm, and height 12 mm to manufacture specimens. And, for the specimen, electric conductivity and Seebeck coefficient were measured using ZEM-3(Ulvac-Rico, Inc) in the range of 50° C. to 500° C.

(17) And, using the measured electric conductivity, Seebeck coefficient, and the thermal conductivity of Experimental Example 1 explained above, thermoelectric figure of merit(ZT) was calculated through the following Mathematical Formula 1.
ZT=σS.sup.2T/K  [Mathematical Formula 1]

(18) wherein, ZT denotes thermoelectric figure of merit, σ denotes electric conductivity, S denotes Seebeck coefficient, T denotes temperature, and K denotes thermal conductivity.

(19) TABLE-US-00002 TABLE 2 Temper- Thermoelectric figure of merit ature Example Comparative Example (° C.) 1 2 3 4 1 2 3 50 0.26 0.26 0.27 0.26 0.18 0.17 0.25 100 0.36 0.36 0.36 0.35 0.25 0.23 0.34 200 0.57 0.57 0.59 0.57 0.40 0.39 0.54 300 0.81 0.80 0.84 0.81 0.58 0.57 0.76 400 1.04 1.04 1.08 1.04 0.76 0.76 0.98 500 1.24 1.25 1.27 1.24 0.93 0.92 1.18

(20) As the results of experiments, as shown in FIG. 2, the compound semiconductors of Examples 1 to 4 exhibited high thermoelectric figures of merit over the whole temperature measurement sections, compared to Comparative Example 1 to 3, due to lowered lattice thermal conductivity.