JPS588593B2 - netsudensoshi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermoelectric element that has good thermoelectric power and electrical conductivity and can exhibit stable performance up to 1,500° C. in an oxidizing atmosphere.

Conventionally used thermoelectric elements include PbTe, GeTe,
Bi2Te3, Sb2Te3, Bi2Se, AgSbT
There are devices that use alloys such as e2, but when using these for thermoelectric power generation, the maximum operating temperature does not reach 1,000℃, and these elements change over time at high temperatures, so it is difficult to actually use them. The maximum temperature reached is only about 500°C.

Generally, thermoelectric power generation efficiency η is expressed by the following equation.

Here, Th is the absolute temperature on the high temperature side, Tc is the absolute temperature on the low temperature side, m = R/r, R is the external resistance, r is the internal resistance of the thermoelectric element, Z = σα2/K is the figure of merit, and σ is the conductivity. rate, α is thermoelectric power, and K is thermal conductivity.

According to equation (1), in order to increase the thermoelectric generation efficiency η, it is obvious that T
It is necessary that the value of h be large.

However, as mentioned above, the conventional thermoelectric element has a
Since it cannot be used above 0°C, it is not possible to increase the temperature on the high temperature side, and therefore it has been impossible to increase the thermoelectric power generation efficiency η.

The present invention solves the above-mentioned drawbacks of the conventional elements, has good thermoelectric power and electric conductivity, and has a
It was developed to provide a thermoelectric element that can exhibit stable performance up to ℃. A compact of cerium dioxide containing 0.1 to 5 mol % in the form of metal or 0.1 to 10 mol % in the form of niobium or vanadium pentoxide for niobium or vanadium is placed in vacuum or in a neutral atmosphere. An N-type thermoelectric element is characterized in that it is made of a sintered body obtained by firing at a temperature of 100 nm.

In the present invention, the tungsten is used in the form of metal at 0.0%.
The green compact of cerium oxide containing 1 to 5 mol % may further contain 0.1 to 10 mol % of niobium or vanadium in the form of niobium pentoxide or vanadium pentoxide. It is also possible for the compact of cerium dioxide containing 0.1 to 5 mol % in the form of niobium or vanadium in the form of niobium pentoxide or vanadium pentoxide, respectively, to contain 0.1 to 10 mol % of niobium or vanadium.

In the present invention, such a green compact of cerium dioxide is fired in a vacuum or in a neutral atmosphere to form a sintered body.
The molding pressure when making the above green compact is 500 to 1,200
Kg/cm2 is preferable, and the firing temperature of the green compact is preferably in the range of 1,300 to 1,500°C.

The element of the present invention made of the sintered body thus obtained is mainly composed of metal oxides, and even if it contains tungsten or molybdenum in the form of metal, the tungsten or molybdenum forms a stable solid solution form by firing. Therefore, it exhibits stable performance even in an oxidizing atmosphere of 1,500°C, and has a thermoelectric capacity α of 500 μV/°K, which is much higher than conventional elements, and a figure of merit Z at 1,500°C.
Excellent N of 0.4 to 0.5 x 10-4°K-1
It is a type thermoelectric element.

The content of tungsten or molybdenum in the cerium dioxide compact of the present invention is required to be in the range of 0.1 to 5 mol% in the form of metal, and the content is 0.1 mol% or less or 5 mol% or less. Above mol%, the performance index decreases.

In addition, the content of niobium or vanadium is required to be in the range of 0.1 to 10 mol% in the form of niobium pentoxide or vanadium pentoxide, and the content is 0.1 mol% or less or 10 mol% or more. In this case, the figure of merit similarly decreases.

Since the element of the present invention is mainly composed of cerium dioxide, which has a low unit price, as a raw material, it is cheaper than conventional elements, which have a high unit price of raw materials, and can be manufactured easily, so it is extremely advantageous in terms of cost.

Due to the above characteristics, the element of the present invention enables highly efficient thermoelectric power generation when combined with a suitable P-type thermoelectric element.

As described above, the present invention has a thermoelectric power of 500 μV/°K, which is much higher than that of conventional elements, and has good electrical conductivity, and exhibits stable performance up to 1,500°C even in an oxidizing atmosphere. It provides an extremely inexpensive thermoelectric element, and its industrial value is extremely large.

EXAMPLES Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 Tungsten metal was mixed with cerium dioxide in the form of powder as shown in Table 1, thoroughly mixed in a pot mill, and 1,000
A green compact was formed by pressure molding at a pressure of kg/cm 2 , and this green compact was fired at 1,400° C. for 3 hours in an argon gas atmosphere to obtain a sintered body.

The electrical conductivity σ, thermoelectric power α, and thermal conductivity K of this sintered body were measured in air from room temperature to 1,500° C. by conventional methods, and the figure of merit Z=σα2/K was determined from these measured values.

Table 1 shows the figures of merit Z1500 and Z1000 at 1,500°C and 1,000°C for each sample, respectively.

Table 1 shows that these sintered bodies have excellent performance as thermoelectric elements.

These sintered bodies were heated in air at a temperature of 1,500° C. for one week, but the above performance did not change and remained stable.

Example 2 Metallic molybdenum was mixed with cerium dioxide in the form of powder as shown in Table 2, and treated in the same manner as in Example 1 to obtain a sintered body.

The electrical conductivity σ, thermoelectric power α, and thermal conductivity K of these sintered bodies were measured in the same manner as in Example 1 at 1,500°C and 1,
Figure of merit Z1 500 and Z100 at 000℃
0 are shown in Table 2.

Table 2 shows that these sintered bodies exhibit excellent performance as thermoelectric elements.

These sintered bodies were heated in air at a temperature of 1,500° C. for one week, but the above performance did not change and remained stable.

Example 3 Niobium pentoxide was mixed with cerium dioxide in the form of powder as shown in Table 3, and treated in the same manner as in Example 1 to obtain a sintered body.

The electrical conductivity σ, thermoelectric power α, and thermal conductivity K of these sintered bodies were measured in the same manner as in Example 1 at 1,500°C and 1,
Pouring index Z1500 and Z1000 at 000℃
are shown in Table 3.

Table 3 shows that these sintered bodies have excellent performance as thermoelectric elements.

*These sintered bodies were heated in air at a temperature of 1,500°C for one week, but the above performance remained unchanged and stable.

Example 4 Vanadium pentoxide was mixed with cerium dioxide in powder form as shown in Table 4, and treated in the same manner as in Example 1 to obtain a sintered body.

The electrical conductivity σ, thermoelectric power α, and thermal conductivity K of these sintered bodies were measured in the same manner as in Example 1 at 1,500°C and 1,
Figures of merit Z1500 and Z100 at 000℃
0 are shown in Table 4.

Table 4 shows that these sintered bodies have excellent performance as thermoelectric elements.

These sintered bodies were heated in air at a temperature of 1,500°C for one week, but the above performance did not change and remained stable.

Example 5 Cerium dioxide, metallic tungsten, and niobium pentoxide were blended in powder form as shown in Table 5, and treated in the same manner as in Example 1 to obtain a sintered body.

The electrical conductivity σ, thermoelectric power α, and thermal conductivity K of these sintered bodies were measured in the same manner as in Example 1.
The figures of merit Z1500 and Z1000 at 0°C are shown in Table 5, respectively.

Next, Fig. 1 shows the above sintered body at 1,500°C and 1,000°C when niobium pentoxide was kept constant at 1 mol%, metallic tungsten was varied from 0 to 15 mol%, and the balance was cerium dioxide. The figures of merit at °C are shown by dotted lines and solid lines, respectively.

Furthermore, Fig. 2 shows the above sintered body at 1,500°C when metallic tungsten was kept constant at 2 mol%, niobium pentoxide was varied from 0 to 15 mol%, and the balance was cerium dioxide.
and the figure of merit at 1,000°C are shown by dotted lines and solid lines, respectively.

Further, FIG. 3 shows the relationship between thermoelectric power α and temperature for sample 13.

From Table 5, Figures 1, 2, and 3 above, it is clear that tungsten is contained in the form of metal in an amount of 0.1 to 5 mol %, and niobium is contained in the form of niobium pentoxide as 0.1 to 10 mol %. It is clear that the sintered body containing cerium dioxide has excellent performance as a thermoelectric element.

Furthermore, these sintered bodies were heated in air at a temperature of 1,500° C. for one week, but the above-mentioned performance did not change* and was stable.

Example 6 Cerium dioxide, molybdenum metal, and niobium pentoxide were blended in powder form as shown in Table 6, and treated in the same manner as in Example 1 to obtain a sintered body.

The electrical conductivity σ, thermoelectric power α, and thermal conductivity K of these sintered bodies were measured in the same manner as in Example 1 at 1,500°C and 1,
Figures of merit Z1500 and Z1 at 000°C
000 are shown in Table 6.

Next, Figure 4 shows the sintered bodies at 1,500°C and 1% when niobium pentoxide was constant at 1 mol%, metal molybdenum was varied from 0 to 15 mol%, and the balance was cerium dioxide.
,000°C are shown by dotted lines and solid lines, respectively.

Furthermore, Fig. 5 shows that the amount of metal molybdenum is constant at 2 mol%,
The figures of merit of the sintered body at 1,500°C and 1,000°C are shown by dotted lines and solid lines, respectively, when niobium pentoxide is varied from 0 to 15 mol% and the remainder is cerium dioxide.

Further, FIG. 6 shows the relationship between thermoelectric power α and temperature for sample 18.

From Table 6, Figure 4, Figure 5, and Figure 6 above, it can be seen that it contains 0.1 to 5 mol% of molybdenum in the form of metal, and 0.1 to 10 mol% of niobium in the form of niobium pentoxide. It is clear that the sintered body containing cerium dioxide has excellent performance as a thermoelectric element.

In addition, these sintered stocks were heated at 1,500℃ in air.
Although it was heated at a temperature of 1 week, the above performance did not change and remained stable.

Example 7 Cerium dioxide, metallic tungsten, and vanadium pentoxide were blended in powder form as shown in Table 7, and treated in the same manner as in Example 1 to obtain a sintered body.

The electrical conductivity σ, thermoelectric power α, and thermal conductivity K of these sintered bodies were measured in the same manner as in Example 1 at 1,500°C and 1,0°C.
Figures of merit Z1 500 and Z1000 at 00°C
are shown in Table 7.

Next, in Figure 7, vanadium pentoxide is kept constant at 1 mol%,
The figures of merit of the sintered body at 1,500° C. and 1,000° C. are shown by dotted lines and solid lines, respectively, when the tungsten metal is varied from 0 to 15 mol% and the remainder is cerium dioxide.

Furthermore, Fig. 8 shows the sintered body at 1,500°C when metallic tungsten was kept constant at 2 mol%, vanadium pentoxide was varied from 0 to 15 mol%, and the balance was cerium dioxide.
and the figure of merit at 1,000°C are shown by dotted lines and solid lines, respectively.

Further, FIG. 9 shows the relationship between thermoelectric power α and temperature for sample 23.

Table 7, Figures 7, 8 and 9 above contain 0.1 to 5 mol % of tungsten in the form of metal and 0.1 to 10 mol % of vanadium in the form of vanadium pentoxide. This shows that a sintered body made of cerium dioxide has excellent performance as a thermoelectric element.

Furthermore, these sintered bodies were heated in air at a temperature of 1,500° C. for one week, but the above-mentioned performance did not change and remained stable.

Example 8 Cerium dioxide, metal molybdenum, and vanadium pentoxide were blended in powder form as shown in Table 8, and treated in the same manner as in Example 1 to obtain a sintered body.

The electrical conductivity σ, thermoelectric power α, and thermal conductivity K of these sintered bodies were measured in the same manner as in Example 1 at 1,500°C and 1,0°C.
Table 8 shows the figures of merit Z1500 and Z1000 at 00°C.

Next, Figure 10 shows the sintered bodies at 1,500°C and 1,000°C when vanadium pentoxide was kept constant at 1 mol%, metal molybdenum was varied from 0 to 15 mol%, and the balance was cerium dioxide. The figures of merit are shown by dotted lines and solid lines, respectively.

Furthermore, Fig. 11 shows the above sintered body of 1,50% when metal molybdenum is kept constant at 2 mol%, vanadium pentoxide is varied from 0 to 15 mol%, and the balance is cerium dioxide.
The figures of merit at 0°C and 1,000°C are shown by dotted lines and solid lines, respectively.

Further, FIG. 12 shows the relationship between thermoelectric power α and temperature for sample 28.

The above Tables 8, 10, 11 and 12 contain 0.1 to 5 mol% of molybdenum in the form of metal and 0.1 to 10 mol% of vanadium in the form of vanadium pentoxide. This shows that a sintered body made of cerium dioxide has excellent performance as a thermoelectric element.

Further, these sintered bodies were heated in air at a temperature of 1,500° C. for one week, but the above-mentioned performance did not change and remained stable.

[Brief explanation of the drawing]

Figure 1 shows 1,500% of the sintered body obtained by firing the green compact when niobium pentoxide was kept constant at 1 mol%, metallic tungsten was varied from 0 to 15 mol%, and the balance was cerium dioxide. Figure 2 shows the relationship between the mol% of metallic tungsten and the figure of merit at 1,000°C and 1,000°C.
1,50% of the sintered body obtained by firing the green compact when the powder was changed to 15 mol% and the remainder was cerium dioxide.
Mol% of niobium pentoxide at 0°C and 1,000°C
Figure 3 is a diagram of the relationship between temperature and thermoelectric power α of sample 13 of Example 5, Figure 4 is a diagram of the relationship between niobium pentoxide and the figure of merit.
The mole ratio of metal molybdenum at 1,500°C and 1,000°C of the fired sintered compact of the green compact when the mol% is constant and the metal molybdenum is varied from 0 to 15 mol% and the balance is cerium dioxide. The relationship diagram with the figure of merit, Figure 5, is obtained by sintering a compact when the mole ratio of metal molybdenum is constant at 2, niobium pentoxide is varied from 0 to 15 mol%, and the balance is cerium dioxide. 1 of the sintered body,
A diagram of the relationship between the molar ratio of niobium pentoxide and the figure of merit at 500°C and i,ooo°C. Figure 6 is a diagram of the relationship between temperature and thermopower α of sample 18 of Example 6. Figure 7 is a diagram of the relationship between the temperature and thermopower α of sample 18 of Example 6. Vanadium is kept constant at 1 mol%, and metallic tungsten is kept at 0 to 1.
1,500% of the sintered body obtained by firing the green compact when the powder was changed to 5 mol% and the remainder was cerium dioxide.
Figure 8 shows the relationship between mol% of metallic tungsten and figure of merit at ℃ and 1,000℃, with tungsten metal constant at 2 mol% and vanadium pentoxide from 0 to 15 mol%.
A diagram of the relationship between the mol% of vanadium pentoxide and the performance index at 1,500 °C and 1,000 °C of a sintered body obtained by firing a green compact when the balance is changed to cerium dioxide, Figure 9 is a diagram of the relationship between the temperature and thermoelectric power α of Sample 23 of Example 7, and Figure 10 shows the relationship between the temperature and thermoelectric power α of Sample 23 of Example 7, and Figure 10 shows the relationship between vanadium pentoxide at 1 mol%, metal molybdenum varying from 0 to 15 mol%, and the remainder being carbon dioxide. The sintered body obtained by firing the green compact when cerium is used at 1,500℃ and
Figure 11 shows the relationship between mole% of molybdenum metal and performance index at 000°C, with molybdenum metal constant at 2 mole% and vanadium pentoxide varied from 0 to 15 mole%.
Figure 12 is a diagram of the relationship between the mol% of vanadium pentoxide and the performance index at 1,500°C and 1,000°C of the sintered body obtained by firing the green compact when the balance is cerium dioxide. FIG. 6 is a diagram showing the relationship between temperature and thermoelectric power α of sample 28 of Example 8.

Claims (1)

[Claims] 1. One selected from the group consisting of tungsten, molybdenum, niobium and vanadium, with 0.1 to 5 mol% of tungsten or molybdenum in the form of metal.
, and for niobium or vanadium, it is a sintered body obtained by firing a green compact of cerium dioxide containing 0.1 to 10 mol% in the form of niobium pentoxide or vanadium pentoxide in a vacuum or neutral atmosphere. An N-type thermoelectric element characterized by the following. 2 The green compact of cerium dioxide containing 0.1 to 5 mol% of tungsten in the form of metal further contains 0.1 to 10 mol% of niobium or vanadium in the form of niobium pentoxide or vanadium pentoxide, respectively. N-type thermoelectric element according to scope 1. 3 The green compact of cerium dioxide containing 0.1 to 5 mol % of molybdenum in the form of metal further contains 0.1 to 10 mol % of niobium or vanadium in the form of niobium pentoxide or vanadium pentoxide, respectively. N in range 1
type thermoelectric element.