P-type semiconductor composed of magnesium, silicon, tin, and germanium, and method for manufacturing the same

Abstract

A manufacturing method for a p-type semiconductor formed by sintering a compound represented by the general chemical formula: Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z (where X+Y+Z=1, X>0, and Y>0, Z>0). The p-type semiconductor has a composition in which X is in the range of 0.00<X0.25, and Z satisfies the relationship: 1.00X+0.40Z2.00X+0.10, where Z>0.00, and Y is in the range of 0.60Y0.95, and Z satisfies either of the relationships: 1.00Y+1.00Z1.00Y+0.75, where 0.60Y0.90 and Z>0.00, and 2.00Y+1.90Z1.00Y+0.75, where 0.90Y0.95 and Z>0.00.

Claims

1. A method for manufacturing a p-type semiconductor composed of magnesium, silicon, tin, and germanium comprising: mixing magnesium, silicon, tin, and germanium as raw materials, obtaining, by liquid-solid reaction, a solid solution of the magnesium, silicon, tin, and germanium mixture represented by the following general chemical formula: Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z, where X+Y+Z=1 and X>0, Y>0, Z>0, and sintering the obtained mixture to produce a p-type semiconductor, the p-type semiconductor represented by the following general chemical formula: Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z, wherein: X is in the range of 0.00<X0.25, and Z satisfies the relationship of 1.00X+0.40Z2.00X+0.10, and Z>0.00, and Y is in the range of 0.60Y0.95, and Z satisfies either of the following relationships: 1.00Y+1.00Z1.00Y+0.75, where 0.60Y0.90 and Z>0.00, and 2.00Y+1.90Z1.00Y+0.75, where 0.90Y0.95 and Z>0.00.

2. The method according to claim 1, wherein Y is in the range of 0.65Y0.90.

3. A p-type semiconductor composed of magnesium, silicon, tin, and germanium, wherein: the p-type semiconductor is manufactured by a liquid-solid reaction of magnesium, silicon, tin, and germanium as raw materials to obtain a material represented by the following general chemical formula: Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z, where X+Y+Z=1 and X>0, Y>0, Z>0, followed by sintering to obtain a the p-type semiconductor, the p-type semiconductor represented by the following general chemical formula: Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z, where: X is in the range of 0.00<X0.25, and Z satisfies the relationship: 1.00X+0.40Z2.00X+0.10, where Z>0.00, and Y is in the range of 0.60Y0.95, and Z satisfies either of the following relationships: 1.00Y+1.00Z1.00Y+0.75, where 0.60Y0.90 and Z>0.00, and 2.00Y+1.90Z1.00Y+0.75, where 0.90Y0.95 and Z>0.00.

4. The p-type semiconductor of claim 3, wherein Y is in the range of 0.65Y0.90.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a process chart for obtaining a p-type semiconductor according to an embodiment of the present disclosure.

(2) FIG. 2A is a table showing compositions of weighed values of p-type semiconductors, and FIG. 2B is a table showing compositions of p-type semiconductors according to the present disclosure.

(3) FIG. 3 is a graph showing X-ray diffraction measurement results of Mg.sub.2Si.sub.0.25Sn.sub.YGe.sub.Z in various p-type semiconductors.

(4) FIG. 4 is a table showing the compositions (weighed values) of Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z and thermoelectric properties thereof at a room temperature in various p-type semiconductors.

(5) FIG. 5A, FIG. 5B, and FIG. 5C are graphs showing the relationships between the Ge composition and the Seebeck coefficient , the thermal conductivity , and the resistivity in various p-type semiconductors.

(6) FIG. 6 is a graph showing the relationship between X and Z in various p-type semiconductors.

(7) FIG. 7 is a graph showing the relationship between Y and Z in various p-type semiconductors.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) The present disclosure provides a p-type semiconductor made of a sintered compact of an intermetallic compound of magnesium (Mg), silicon (Si), tin (Sn), and germanium (Ge), which is represented by the following general chemical formula:

(9) Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z, wherein X+Y+Z=1 and X>0, Y>0, Z>0. The sintered compact of the intermetallic compound is manufactured as follows.

(10) Granular Mg and Sn with a grain size of approximately 2 to 10 mm are prepared, and powdery Si and Ge with a grain size of approximately several tens of m are prepared. Predetermined amounts of these materials are weighed and put into a carbon board. The carbon board is covered with a carbon lid, and heated for 4 hours at an absolute temperature of 1173 K under an atmosphere of 0.1 MPa ArH.sub.2 (3 weight % hydrogen) to cause a liquid-solid reaction.

(11) The obtained solid solution is pulverized into powder with a grain size of 38 to 75 m, and sintered by hot-pressing. The sintering pressure is standardized to 50 MPa and the sintering time is standardized to 1 hour. The sintering temperature was determined according to each Sn composition amount Y. The sintering temperature is set to 1190 K when Y=0, 1040 K when Y=0.60 or 0.65, and 930 K when Y=0.75 or 0.90.

(12) Weighed values (mole ratios) and compositions (mole ratios) of several sintered compacts obtained as described above are shown in the tables of FIG. 2. According to this, the weighed values (FIG. 2A) and the compositions (FIG. 2B) of the sintered compacts are found to have changed little when comparing the amounts of the Mg, Si, Sn and Ge before and after sintering.

(13) Further, in FIG. 3, results of X-ray diffraction measurement of Mg.sub.2Si.sub.0.25Sn.sub.YGe.sub.Z obtained as described above are shown. According to X-ray diffraction, peaks were observed with all of the sintered compacts existing between Mg.sub.2Si and Mg.sub.2Sn having an anti-fluorite structure. Only peaks caused by the anti-fluorite structure were observed, and no peaks were observed with oxides, Mg.sub.2Si, Mg.sub.2Ge, and Mg.sub.2Sn. Based on the data in FIG. 3, it was confirmed that all of the sintered compacts were single-phase. The same results were obtained with other sintered compacts.

(14) Next, the conduction types, the Seebeck coefficients (V/K), the thermal conductivities (W/mK), and the resistivities (m) of various sintered compacts of Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z thus obtained are shown in the table of FIG. 4. In FIG. 5, graphs showing the relationships between the Ge composition and the Seebeck coefficient , the thermal conductivity , and the resistivity are shown.

(15) Next, conduction types of semiconductors with variable values for X and Z based on the results of FIG. 4 are plotted in FIG. 6. Conduction types of these semiconductors in which the values between Y and Z change are plotted in FIG. 7. From these graphs, the conduction type border between the p-type and the n-type is found to have changed linearly. In each graph, indicates p-type, and x indicates n-type.

(16) First, observing the relationship between X and Z in FIG. 6, as a p-type semiconductor, X is in the range of 0.00<X0.25. When X is in this range, a maximum value Z.sub.max and a minimum value Z.sub.min of Z for obtaining a p-type semiconductor change linearly in relation to X. A linear function of Z.sub.max and a linear function of Z.sub.min are respectively obtained as follows:

(17) Z.sub.max=1.00X+0.40

(18) Z.sub.min=2.00X+0.10, where Z.sub.min>0.00.

(19) It is confirmed that, as a p-type semiconductor, X and Z fall within the shaded range shown in FIG. 6, that is, X and Z satisfy the following relationship:

(20) 1.00X+0.40Z2.00X+0.10, where Z>0.00.

(21) Observing the relationship between Y and Z in FIG. 7, as a p-type semiconductor, Y is in the range of 0.60Y0.95. When Y is in this range, a maximum value Z.sub.max and a minimum value Z.sub.min of Z for obtaining a p-type semiconductor change linearly in relation to Y, and a linear function of Z.sub.max and a linear function of Z.sub.min are obtained as follows:

(22) Z.sub.max=1.00Y+1.00, where 0.60Y0.90

(23) Z.sub.max=2.00Y+1.90, where 0.90Y0.95

(24) Z.sub.min=1.00Y+0.75, where Z.sub.min>0.00.

(25) It is confirmed that as a p-type semiconductor, Y and Z fall within the shaded range shown in FIG. 7, that is, Y and Z satisfy the following relationship:

(26) 1.00Y+1.00Z1.00Y+0.75, where 0.60Y0.90 and Z>0.00, or

(27) 2.00Y+1.90Z1.00Y+0.75, where 0.90Y0.95 and Z>0.00.

(28) The present disclosure is applicable to obtaining of a p-type semiconductor composed of Mg.sub.2Si.sub.XSn.sub.YGe.sub.Z.