JPH0684529B2 - Low temperature thermoelectric material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL FIELD OF USE The present invention is a Bi that exhibits high performance at low temperatures (77 to 200 ° K).
-For more details on Sb-based thermoelectric materials and their manufacturing methods, it is useful as a leg material for electronic cooling modules that utilize the Bertier effect, or a leg material for cold heat (source) power generation modules that utilize the Seebeck effect. The present invention relates to a thermoelectric material composition of a p-type Bi—Sb alloy which has never been obtained, and a method for producing the same.

Conventional technology Bi-Sb alloys are n-type semiconductors with bandgap of about 0.015eV in a limited range in low temperature range (for example, Bi ₉₅ Sb _{5 to} Bi ₈₀ Sb ₂₀ at 4.2 ° K), which is excellent in low temperature range. It is widely known that the Berttier effect is exhibited (see, for example, Japanese Patent Publication No. 38-15421).

This n-type Bi-Sb alloy is actually an intrinsic semiconductor, and there are almost the same number of electrons and holes as carriers. However, since electron mobility is higher than hole mobility, n-type conduction is assumed (for example, T.AONO and S.AIZAWA).
"Study on Thermal Gap of Bi-Sb Alloys" Tokyo Denki
See Univ.).

In addition, a single crystal B containing several 100 ppm of Group IV elements such as Sn and Pb
In i-Sb, p-type conduction is exhibited in a so-called impurity region at extremely low temperature, but it is reported that the i-Sb inverts to n-type as the temperature rises (for example, W. Yim and A. Amith, Solid-State Electroni
cs, 1972, Vol.15, p.1141-1165).

Therefore, it is not possible to manufacture from a Bi-Sb alloy that becomes p-type from cryogenic temperature to near room temperature by the Britzmann method or zone melting method for the purpose of producing a single crystal. -Sb alloys have not yet been discovered and manufactured. In the following description, only Bi-Sb that becomes p-type from cryogenic temperature to room temperature will be referred to as p-type Bi-Sb alloy.

Problems to be Solved by the Invention As described above, the Bi-Sb alloy is widely known as a thermoelectric material that exhibits high performance at low temperatures, but since only n-type materials can be produced, the legs of the electronic cooling module are not known. At present, it has not been put to practical use as a material.

Therefore, an object of the present invention is to provide a Bi-Sb alloy that becomes p-type from cryogenic temperature to room temperature and a method for producing the same.

Another object of the present invention is to provide a leg member of an electronic cooling module,
Bi-S, which is useful as a leg material for cold heat (source) power generation modules and has high performance at low temperatures, for example, 77 to 200 ° K.
It is to provide a b-type thermoelectric material and a method for manufacturing the same.

Means for Solving the Problems According to the research conducted by the present inventor, it was found that the following composition was required to obtain a p-type Bi—Sb alloy.

{(Bi _100- xSbx) _100- y ▲ E ^II _y ▼} _100- z ▲ E ^I _Z ▼ Here, E ^I represents a Group II or IV group element, E ^II represents a IV / VI group element, x is 5 to 20, y is 0 to 20, and z is 0.05 to 10. (However, in order to obtain the above-mentioned alloy composition, it may be necessary to prepare a forced solid solution from the state of being completely in one liquid phase at a temperature of 350 to 800 ° C. by using a quenching roll method or the like.) That is, the Bi—Sb thermoelectric material of the present invention is a Bi _100- xSbx (where x = 5 to 5) that serves as an intrinsic semiconductor as a Bi—Sb master alloy.
20) is adopted, and a group II or p-type dopant is used.
The group IV element is added in an amount of 0.05 to 10 at%, and in order to improve the performance of the thermoelectric material in practical use, 0 to 20 at% of the group IV / VI element is added as necessary. When the group IV element is added as the p-type dopant, it is not necessary to add the group IV / VI element.

The p-type Bi-Sb alloy is obtained by solidifying a Bi-Sb alloy in a molten state at a cooling rate capable of becoming a non-equilibrium phase according to the method of the present invention. Specifically, in the apparatus as shown in FIG. 1, the molten metal reservoir 4 is loaded with the Bi—Sb alloy 3 and heated by the high frequency coil 2 to bring the Bi—Sb alloy into a molten state. On the other hand, the metal roll 1 (φ200 mm, width of about 20 mm) is rotated at 500 to 4000 rpm, and the molten metal is jetted from the molten metal reservoir 4 by the inert gas pressure (0.5 to 4 kg / cm ² ) to be cooled and solidified. In addition, without using the quenching roll method,
It would be possible to make p-type Bi-Sb alloys by rapid solidification methods (eg quench powders) that allow the addition of more p-type dopants than equilibrium solidification. Further, in the rapid roll method, unless the manufacturing conditions are set in the range of a roll speed of 500 to 4000 rpm and a gas injection pressure of 0.5 to 4 kg / cm ² , a high quality quenching film cannot be obtained, and therefore, preferably in the above range. Set.

In the conventional Britzmann method or zone melting method, p
Although the type dopant can be added only in an amount (a few hundreds of ppm) that is solid-solved in equilibrium solidification, the above-described method of the present invention makes it possible to add more p-type dopant than the equilibrium solidification amount. P-type Bi that could not be manufactured
-Sb alloy can be manufactured.

That is, as explained in the section of the prior art, the Bi—Sb alloy to which the group IV element is added by several hundred ppm by equilibrium solidification is inverted to p → n type with temperature rise (see FIG. 4). According to the above, by adding 0.05 to 10 at% of III or IV group element as a p-type dopant to the intrinsic semiconductor of Bi _100- xSbx (x = 5 to 20), p-type conduction is shown at 77 ° K to room temperature. Bi-
An Sb alloy is obtained (see Figures 2, 5-7).

This is because, for example, in the case of a Bi-Sb alloy in which the p-type dopant Sn is added by an equilibrium solidification amount or less by a conventional method, the p-type dopant Sn has a higher hole concentration than the electron concentration at a low temperature, but the p-type dopant becomes p-type. , As the concentration of holes and electrons becomes almost equal as the temperature rises, the electrons with high mobility dominate conduction and invert to n-type (see FIG. 4). Group IV elements such as Pb other than Sn have also been reported (eg GESmith and R. Wolfe, Journal of
applied Physics, Vol.33,841 (1962)). On the other hand, as in the present invention, p of 0.05 to 10 at% above the equilibrium coagulation amount is used.
When the type dopant is added, the hole concentration is higher than the electron concentration before room temperature even near room temperature due to the added group III element (Al, Tl, etc.) or group IV element (Sn, Pb, etc.). , P-type conduction.

If the addition amount of the group III element or the group IV element is less than 0.05 at%, p-type conductivity will not be exhibited up to around room temperature, while it is not practically appropriate to add the above element more than 10 at%. (Practically, the carrier concentration is controlled to about 10 ¹⁹ to 10 ^20. ) In addition, in the p-type Bi-Sb alloy of the present invention, in order to reduce the thermal conductivity of the thermoelectric material in order to improve the performance. In addition, IV / VI group elements may be added to the extent that p-type conduction is not impaired. As a matter of course, the IV / VI group element may not be added. IV
The addition amount of the group VI element exceeding 20 at% is not preferable because the thermoelectric power of the Bi-Sb alloy is impaired.

Examples Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. Needless to say, the present invention is not limited to the examples below.

Example 1 1 at% of Sn was added as a p-type dopant to a Bi-Sb alloy having a composition of Bi ₈₈ Sb ₁₂ , and the mixture was heated to about 600 ° C to obtain a uniform liquid phase state (in an Ar atmosphere of about 1 atm). From this state, about 10
The molten metal was sprayed at a gas injection pressure of about 1.0 kg / cm ² onto a Cu roll rotating at 00 rpm to prepare a thin film having a length of about 20 mm, a width of about 2 mm and a thickness of about 30 μ.

When the Seebeck constant of the obtained film was measured, the results shown in FIG. 2 were obtained.

Comparative Example 1 A quenched thin film having a composition of Bi ₈₈ Sb ₁₂ was prepared in the same manner as in Example 1, and the Seebeck constant was measured. The results shown in FIG. 3 were obtained.

Comparative Example 2 An alloy having the same composition as in Example 1 was brought into a uniform liquid phase state at about 600 ° C. and solidified by the Britzmann method at a temperature gradient of about 40 ° C./cm and a solidification rate of 0.75 mm / hr to obtain a diameter of 10 mm and a length of 10 mm. 150mm Bi
-The Sb element was produced.

When the Seebeck constant in the central part of the device was measured,
The results shown in the figure were obtained.

As is apparent from FIG. 2, the Seebeck constant of the alloy thin film prepared in Example 1 (thin film obtained by solidifying the molten metal having the composition of (Bi ₈₈ Sb ₁₂ ) ₉₉ Sn ₁ by the sudden method) is 77 °. Positive from K to room temperature, that is, p-type conduction. On the other hand, as shown in FIG. 3, the alloy having the composition of Bi ₈₈ Sb ₁₂ of Comparative Example 1 has a negative Seebeck constant from 77 ° K to room temperature, that is, has an n-type. (This also applies to an alloy of Bi _100- xSbx, x = 5 to 20 containing no p-type dopant.) On the other hand, in Comparative Example 2, a molten metal having a composition of (Bi ₈₈ Sb ₁₂ ) ₉₉ Sn ₁ was used. Device manufactured by Britzmann method (actually,
When manufactured by the Britzmann method, Bi ₈₈ Sb ₁₂ has Sn of about 0.03 at.
%, The composition of (Bi ₈₈ Sb ₁₂ ) ₉₉ Sn ₁ cannot be prepared, and the single crystal containing Bi ₈₈ Sb ₁₂ containing 0.03 at% Sn is shown in Fig. 4. As shown, the temperature changes from positive to negative, that is, from p-type to n-type.

Example 2 A quenched thin film having a composition of {(Bi ₈₈ Sb ₁₂ ) ₉₅ (PbSe) ₅ } ₉₉ Ga ₁ was prepared in the same manner as in Example 1, and the Seebeck constant was measured. The results shown in FIG. 5 were obtained. was gotten.

Example 3 An example thin film having a composition of {(Bi ₈₈ Sb ₁₂ ) ₉₅ (PbTe) ₅ } ₉₉ Tl ₁ was prepared in the same manner as in Example 1, and the Seebeck constant was measured. The result is shown in FIG. Results were obtained.

Example 4 A quenched thin film having a composition of {(Bi ₈₈ Sb ₁₂ ) ₉₄ (PbSe) ₆ } ₉₉ Al ₁ was prepared in the same manner as in Example 1, and the Seebeck constant was measured. The results shown in FIG. 7 were obtained. was gotten.

Effects of the Invention As described above, according to the quenching method of the present invention, Bi _100- xSbx (x = 5 to 2) becomes an intrinsic semiconductor as a Bi-Sb based master alloy.
0) contains a group III or IV element as a p-type dopant of 0.05
Bi-Sb alloy with ~ 10at% added was obtained.
It is a p-type Bi-Sb alloy that shows p-type conductivity from extremely low temperatures (77 ° K) to near room temperature, which could not be produced conventionally. Therefore, by combining the p-type Bi-Sb alloy of the present invention with the conventional n-type Bi-Sb alloy and using it as the leg material of the electronic cooling module, the maximum cooling by electronic cooling using the current BiTe-based material is achieved. Possible temperature about -100 ℃ (marlow M16030) at a stretch -200
It is a great advantage that it can be lowered to near ℃,
Applied effects can be obtained.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of an apparatus for carrying out the method of the present invention, and FIG. 2 is a p obtained in Embodiment 1 of the present invention.
4 is a graph showing the temperature change of the Seebeck constant of the n-type Bi-Sb alloy thin film, and FIG. 3 is a graph showing the temperature change of the zebeck constant of the conventional n-type Bi-Sb alloy thin film obtained in Comparative Example 1.
The figure is a graph showing the temperature change of the Seebeck constant of the Bi-Sb element produced by the Britzmann method, and FIGS. 5 to 7 show the Seebeck constant of the p-type Bi-Sb alloy thin films produced in Examples 2 to 4. It is a graph which shows a temperature change. 1 is a metal roll, 2 is a high frequency coil, 3 is a Bi-Bb alloy, and 4 is a molten metal pool.

Claims (4)

[Claims] 1. {(Bi _100- xSbx) _100- y ▲ E ^II _y ▼} _100- z
▲ E ^I _z ▼ (where E ^I is a group III or IV element, and E ^II is IV.
VI group element, x is 5 to 20, y is 0 to 20, z is 0.05 to
Is 10. ) A Bi-Sb-based thermoelectric material having the composition shown in. 2. The thermoelectric material according to claim 1, wherein E ^I is a Group IV element and y is 0 in the above formula. 3. A Bi-Sb alloy characterized in that a Bi-Sb alloy in a molten state is solidified at a cooling rate capable of becoming a non-equilibrium phase.
Of manufacturing thermoelectric material. 4. A Bi-Sb alloy in a molten state is added in an amount of 500 to 4000.
The method according to claim 3, wherein cooling and solidification is carried out by spraying at a spray pressure of 0.5 to 4 kg / cm ² onto a metal roll rotating at prm.