JP2549633B2 - High temperature thermistor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high temperature thermistor, and more particularly to a high temperature thermistor which is preferably used at a high temperature of about 1000 ° C.

2. Description of the Related Art Thermistors are ceramic temperature sensors that utilize the temperature dependence of electrical resistance and are widely used for temperature measurement and temperature control. The operating temperature of a thermistor is determined by the stability of its operating resistance and resistance value, and a high temperature thermistor is usually used in the temperature range of 300 to 1000 ° C. There are various types of high temperature thermistor elements, such as spinel type, perovskite type, zirconia type and corundum type, and various types of high temperature thermistors having different compositions have been developed (for example, JP-A-60-37101). ).

By the way, since the high temperature thermistor is also used in a device produced in a relatively large amount such as detecting the temperature of exhaust gas in an automobile internal combustion engine, the range of choice is limited due to the availability of materials at any given time. In order to expand it, development of more kinds of high temperature thermistors was desired.

The present invention has been made in view of the background as described above, exhibits an appropriate resistance value even in a high temperature range of up to 1000 ° C., and has little resistance change over time, and is thermally and chemically stable. It is a high temperature thermistor, and an object thereof is to provide a high temperature thermistor having a composition different from that of a conventional one.

Means for Solving Problems The above object is composed of SiC and MO (MO is a metal oxide of zirconium or yttrium) and is represented by the general formula (1-x) SiC + xMO (where 0.05 ≦ x ≦ 0.7) A high temperature thermistor according to the invention consisting of a composition is achieved.

Here, when x is less than 0.05, the sinterability of the green sheet is poor, and the difference in expansion coefficient between the electrode and dangsten (W) or molybdenum (Mo) is large. Delamination occurs between the two and becomes difficult to put into practical use.

On the other hand, when x exceeds 0.7, the resistance value of the high temperature thermistor changes with time at 800 ° C. (operating range), and it becomes difficult to put it into practical use.

On the other hand, according to the high temperature thermistor of the present invention in which 0.05 ≦ x ≦ 0.7, the thermistor constant is large as shown in the table below, and the rate of change in resistance value in the high temperature region is 1.0% or less. It is possible to obtain a high temperature thermistor which is small and is stable both thermally and chemically.

Practical example An example is given below.

SiC, zirconium oxide (ZrO ₂ ), yttria (Y
₂ O ₃ ) is weighed so that the composition of the A sheet in Table 1 below is obtained, and 10% of an organic binder is added thereto,
Mix to prepare a slurry. A green sheet having a thickness of 100 μm was produced from this by a doctor blade method. This green sheet was cut into a 3 cm × 4 cm square, and tungsten (W) electrode paste was applied to both sides of the green sheet to obtain an A sheet. On the other hand, a powder containing Al ₂ O ₃ and ZrO ₂ —Y ₂ O ₃ as main components was mixed with a 10% organic binder and a solvent to prepare a slurry, and the same thickness as the A sheet was measured by the doctor blade method.
A 100 μm green sheet was prepared. This was used as a B sheet, and through holes corresponding to the number of electrodes were formed in the B sheet. Next, sandwich both sides of A sheet with B sheet at 50 ℃, 30
Both sides of the A sheet were crimped with the B sheet at sec, 5 t / cm ² .
This pressure-bonded sheet was cut so that each electrode was located at the center, and chips were made. The chips were fired at 1500 to 1700 ° C. in a neutral or reducing atmosphere such as nitrogen (N ₂ ) or argon (Ar) or hydrogen (H ₂ ). A 3 mm × 3 mm square Pt electrode paste was applied to both sides of the chip after firing, and the Pt electrode paste was poured into the through holes of the chip and electrically connected to the W electrode inside the chip. Next, samples No. 2 to 5 and 7 in Table 1 baked at 1100 to 1200 ° C in a neutral atmosphere.
The high temperature thermistor samples shown in FIGS.

The thermistor constant, the resistance value (1800 ° C.) and the rate of change of the resistance value (1000 ° C., 1000 hr) by the aging test of each sample obtained as described above were measured. The results are shown in Table 1.

The high temperature thermistor samples shown as sample Nos. 1 and 6 in Table 1 are shown as comparative examples of this example.

EFFECTS OF THE INVENTION As is clear from the above description and the results shown in Table 1, the high temperature thermistor of the present invention (Sample Nos. 2 to 5, 7 to 9)
Has a large thermistor constant and is excellent in aging characteristics with a rate of change of resistance value of 1.0% or less even when left at a high temperature of 1000 ° C, and the problem that the resistance value is too high and delamination occurs is solved, It is a high temperature thermistor that has excellent thermal and chemical stability and is suitable for high precision requirements.
Since the composition is different from that of the conventional high temperature thermistor, it has an effect of broadening the range of selection.

Continuation of front page (56) References JP-A-60-37101 (JP, A)

Claims (1)

(57) [Claims] 1. A composition comprising SiC and MO (MO is a metal oxide of zirconium or yttrium) and having a composition represented by the general formula (1-x) SiC + xMO (where 0.05 ≦ x ≦ 0.7). High temperature thermistor.