JPS6043882A - P type thermoelectric generating material - Google Patents

Abstract

PURPOSE:To obtain a large output without lowering the thermoelectromotive force of iron silicide by using an alloy or a solid solution in which specific quantities of manganese and aluminum are made to contain in iron silicide. CONSTITUTION:An alloy or a solid solution in which a manganese element and an aluminum element are made to contain in iron silicide in quantities of manganese at an atomic percent of 1.67 and the sum total of manganese and aluminum at an atomic percent of 2.0-4.7 is used. Each raw material of elements, such as iron, metallic silicon (not less than 98% purity), manganese and aluminum is weighed so as to form said composition, and the mixture is melted by using a high-frequency melting furnace, and casted to a mold made of iron, thus manufacturing the iron silicide alloy containing manganese and aluminum. The alloy is changed into powder of several mum by employing a stamp mill and a ball mill made of iron, and the powder is sintered for 3min at 1,060-1,100 deg.C while applying pressure of 250kg/cm<2> in an argon atmosphere, and thermally treated for 50hr at 800 deg.C, thus obtaining a thermoelectric material.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermogenic material, and more particularly to a P-type iron silicide thermoelectric material that can provide a large output.

Thermoelectric materials that directly convert thermal energy into electrical energy have physical properties such as high thermoelectric power (Seebeck number) and low specific resistance and thermal conductivity.
In addition to the above-mentioned physical properties, thermoelectric materials that can be used in high-temperature atmosphere must also have chemical properties such as excellent heat resistance and acid resistance.

A 3d-transition metal silicide can be cited as a material that satisfies such conditions.

Among the silicides, iron silicides are particularly excellent thermoelectric materials in that they have a very large thermoelectromotive force (Patent No. 930733 by the present inventor).

However, the P-type thermoelectric power generation material made of silicide has a relatively high resistivity, and for example, when used as a power source for a hot-air heater that uses gas or oil as a heat source, it is necessary to rotate the motor. It had the disadvantage that it was not suitable for use as a power source for extracting large currents.

It is an object of the present invention to provide a P-type thermoelectric power generation material which eliminates the above-mentioned drawbacks and which can provide a large output by degrading the thermoelectromotive force of iron silicide.

As a result of research to achieve the above object, the present invention has found that an alloy or solid solution containing and having a total amount of 2.0 to 5.4 atoms of iron silicide has the ability to reduce the heat/electromotive force of iron silicide. It was discovered that a large output can be obtained as soon as the material is degraded, and the present invention was completed based on this finding.

The thermoelectromotive force and average specific resistance of the thermoelectric power generation material obtained by setting manganese to 167 atoms in iron silicide (FeSi) and varying the content of ~nganese element and aluminum = :j, element, Table 1 shows the effective maximum yield.

In addition, for comparison, those containing only manganese and those containing small aluminum are also shown.

Table 1 Content (atomic %) Thermoelectromotive force average specific resistance Effective maximum output Mn Δt Total (mV) (Ω, cm) (Wc
m1a! ) These values were taken at a temperature difference of 800° C., and the average resistivity and effective maximum output correspond to the internal resistance and maximum output per unit volume, respectively.

As can be seen from the results shown in Table 1, when the content of manganese element is 1.67 atoms and the content of aluminum element is 0.33 to 303 atoms, the thermoelectromotive force is large without deterioration. Output is obtained, but when the content of the aluminum element exceeds 3.03 atomic ratios, the thermoelectromotive force and output decrease. Still, the content of aluminum 9com element is 0.3
3 atoms (less than 1% and containing only manganese element), the thermoelectromotive power, power and output are consistent, and the aluminum
The effect of containing mu elements does not appear. Therefore, the total content of Ma-Gal elements and A-Mi-Qm elements is 2.
It needs to be in the range of 0 to 4.7 atoms.

The P-type thermoelectric power generation material of the present invention can be obtained in the shape of a cylinder or a prism by a general casting method, but if low-purity raw materials (recycled steel, metal silicon) are used, It is extremely difficult to obtain a material 9 without any fine cracks or bubbles. Therefore, it is preferable to manufacture such a product by a powder metallurgy method. The following examples were performed using powder metallurgy methods.

Example Each raw material of iron, metallic silicon (purity of 98 cm or more), manganese, and aluminum = 'ci4-m was mixed with F e O, 95M n
o, o s 5j2-zA7. Weigh it so that it has the composition Z, and melt this mixture 1 using a high frequency melting furnace,
An iron silicide alloy containing 1.67 atoms of manganese element and 0.30 to 300 atoms of aluminum element was prepared by casting into an iron mold. Each of these alloys was made into a powder of several micrometers using an iron stamp mill and a ball mill.

This powder was sintered at 1060-1100°C for 3 minutes under an argon atmosphere under a pressure of 250 Kv/ca, and subsequently heat-treated at 800°C for 50 hours to form a thermoelectric material (5x
B x 25 +J) was obtained.

The electromotive force, average specific resistance, and effective maximum output of the thermoelectric material were as shown in Table 1.

According to the thermal lightning generation material of the present invention, by including a specific amount of manganese and artanium in the iron silicide, it is possible to obtain an excellent thermal electromotive force and output.

Claims (1)

[Claims] A thermoelectric power generation material made of an alloy or solid solution containing manganese element and aluminum element in iron silicide in an amount of 1.67 atomic ratio of manganese and 20 to 4.7 atomic ratio of manganese and aluminum in total.