JPS6191060A - Thermistor for high temperature - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a high temperature thermistor that can be used in a high temperature range of 400 to 1100°C.

(Prior art) In general, NTC thermistors whose resistance value has a negative temperature coefficient (Negative T@mperature@Coef
fic1@ntThermistor) and the temperature is 1 = I) o exp B (1/'r
There is a relationship: -1/'r (1). Here ρ, ρ0
is the temperature T.

This is a constant called the BViB constant or thermistor constant, which represents the slope of the straight line when blood ρ is plotted against 1/'r.

When trying to measure temperature from changes in the resistance value of a thermistor, as can be seen from the above equation, the larger the B constant, the larger the ratio of change in resistance value to temperature change at a certain temperature, so it is possible to measure temperature changes with good sensitivity. Can be detected. Furthermore, in the above equation, the value of 1/'r decreases rapidly as the value of T increases, that is, as the temperature increases, so in order to accurately detect the temperature especially in a high temperature range, It is necessary to select a material with a large B constant for the thermistor. As such a thermistor, Japanese Patent Application Laid-open No. 48-619
No. 84 has been proposed. This is a zinc oxide sintered body containing predetermined amounts of antimony oxide and conosilt oxide, and its B constant is about 7,000.

However, on the other hand, there is also the problem that a large B constant means that the design usable temperature range becomes narrower than one with a small B constant. Therefore, its purpose in actual use.

A thermistor with an appropriate resistance value and B constant must be selected depending on the application.

Conventionally, as a high temperature thermistor having a spinel crystal structure, Mg(Aj*Cr,Fe)2041
Co(A), Cr, Fe)204*Co(
A), Cr) z04 and LaCr0.5 mixed compositions are known, but these either have a small B constant for a thermistor used in a high temperature range, or even if the B constant is large to some extent, the resistance value is too large. It was so large that it could not be said to be practically satisfactory.

(Problems to be solved by the invention) In a spinel solid solution having a composition of (CoxMg, -x)An204, it is possible to obtain thermistors with various resistance values and B constants depending on the actual purpose and application. be. That is, by changing the ratio of CO and Mg, the (Co, Mg) Al2O4 solid solution was made to exhibit various resistivity values while maintaining a large B constant value.
By replacing aluminum with antimony2, υ
The object is to obtain a thermistor in which the specific resistance value is further reduced and the value of the B constant can be varied within a relatively large range of values.

(Means for Solving the Problems) The present invention provides a spinel solid solution having a composition of (COxMg, -x)Al2O4 (0.1≦x≦0.95), in which aluminum is added at 5b20 to the spinel solid solution.
This is a high temperature thermistor characterized in that the antimony is replaced with 5 to 90 mol of antimony in terms of 3.

MgAj204 generally has a temperature of 107~ at 1000°C.
108Qc! It has a high specific resistance of R and also C0Aj20
4 has a low resistivity of about 10203. Therefore, the specific resistance of (COxMg, -x)Al2O4 can be changed by changing the value of
, 204 to the specific resistance value of C0Aj204.
’ can be used to sequentially decrease the value. Moreover, the value of the B constant in that case is 20.000 or more, specifically 2
Almost no change can be seen around 2,000.

However, in order to provide a practical thermistor for various purposes and applications, K should be determined not only by the specific resistance value but also by B.
The constants must also be traps that can be easily changed as required.

As a result of research to meet this demand, the inventor found that this object could be achieved by substituting aluminum in the solid solution with antimony, thereby completing the present invention.

First, the inventor studied the change in resistivity of spinel type solid solution (CoxMg+-E) A7!204, and found that the value of X was 0.
It was confirmed that it can be implemented within the range of 1 to 0.95. If the value of Moreover, if the value of

In order to obtain a good sintered body and to be able to arbitrarily change the B constant by antimony substitution, the value of X in the chemical formula of the solid solution is preferably in the range of 0.1 to 0.95.

It has also been found that in order to change the B constant, aluminum in the spinel type solid solution can be replaced with 5 to 90 moles of antimony in terms of 5b203. 5b20
When 3 is less than 5 molti, the B constant hardly decreases. Moreover, if 5b203 exceeds 90 molti, it is inappropriate because it will melt during the calcination stage. Further explanation will be given below with reference to Examples.

Example 1 Aj(OH), , Mg(OR)2. CoO, 5b2
Each reagent powder of o3 was blended in the proportions shown in Table 1 to obtain a sintered body.

The manufacturing method is to dry mix the above reagent powders in an alumina automatic mortar for 1 hour, then wet mix for 2 hours using ethanol as a dispersion medium, and finally dry mix for 1 hour before placing them in an aluminum mortar at a temperature of 1200 to 14'00°C. It was calcined for 4 hours. This calcined powder was dry-pulverized for 2 hours in an alumina automatic mortar, and then an aqueous solution of 6% by weight polyvinyl alcohol was added as a binder at a ratio of 0.05 d to powder IP and mixed. The mixture was press-molded into a disk shape with a diameter of 10 m and a thickness of 2 mm at a pressure of 1 ton ~, and
A sintered body was produced by firing in an electric furnace at a temperature of 00°C for 2 hours.

Next, platinum electrodes were baked on both surfaces of this sintered body. The resistivity-temperature characteristics of the element thus obtained were measured in a temperature range of 200 to 1100° C. using a DC stabilized power source and an electrometer. The results are shown in Figure 1.

In addition, in the compounding composition shown in Table 1, Mg(OH)
2. , Lj! (-0H)3 are MgQ, respectively
Shown as the value converted to Aj203, and also CoO and MgO
The total amount of Ano203 and 5b20. The total amount of is 100 molti, and the sum of MgO and Coo and Aj20.
The sum of and 5b20° was made to be 1:1.

Table 1 and Table 2 show the above elements at 1000°C, 700°C, 5
The values of each specific resistance and B constant at 00°C are shown.

Table 2 From Figure 1 and Table 2, by replacing aluminum in (CoxMg, -,)Al2O4 with antimony, the B constant can be changed from 22,000 to nearly half of that, 11,500. reference).

Moreover, the rate of decrease tends to increase as the amount of 5b2o increases. In addition, the specific resistance is 1000℃,
It can be seen that the temperature decreases at both 700°C and 500°C. Furthermore, C and G in Table 1.

From H, it can be seen that as the CoO ratio increases, the effect of lowering the resistivity and B constant due to 5b203 will be greater compared to the case where the CoO ratio (, ) is not increased even when 5b203 is the same at 20 molti. Recognize.

Example 2 Without using °5b205, Ano(OH)3 + Mg(O
H) 2 m Co.

In the same manner as in Example 1 using each reagent (CoXMg,
-x) Al2O4-based sintered body Whole sintered body However, the value of X was varied as shown in Table 3. The obtained sintered body was made into an element in the same manner as in Example 1, and the resistivity-temperature characteristics were measured in the temperature range of 200 to 1100°C. The results are shown in Figure 2. Further, Table 3 shows the specific resistance values and B constants of this element at 1000°C and 700°C.

As is clear from Table 3, Figure 2 and Table 3, as the value of X increases, that is, even if Co increases and Mg decreases,
Although the specific resistance decreases at either 1000° C. or 700° C., the B constant hardly changes at 20.000 or more and especially when X is 0.1 or more.

(Effect of the invention) As explained above, the thermistor ii (
By changing the ratio of Co to Mg and the ratio of υ to sb in CoxMf, -, ) u204 type solid solution, it is possible to easily obtain thermistors with various values of resistivity and B constant. The developed thermistor can be made highly sensitive and practical.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the specific resistance-temperature characteristics of the thermistor according to the present invention. Figure 2 shows (CoxMg, -x)Al2O4
FIG. 3 is a diagram showing specific resistance-temperature characteristics when X of the system sintered body is changed.

Claims (1)

[Claims] In a spinel solid solution with a composition of (Co_xMg_1_-_x)Al_2O_4 (0.1≦x≦0.95), aluminum is added to the spinel solid solution with Sb_2
A high-temperature thermistor characterized in that antimony is substituted with 5 to 90 mol% of O_3.