JPS6143841B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a sintered metal oxide thermistor composition. A thermistor is generally expressed by the resistance-temperature characteristic shown in the following equation, and is a resistor having a negative temperature coefficient of resistance (hereinafter referred to as B constant). R = R _p ExP (B / T - B / T _p ) R = resistance value at temperature T (K) R _p = resistance value at temperature T _p (K) B = temperature coefficient of resistance of thermistor (K) ) These have come to be used in many fields such as temperature compensation of transistor circuits, temperature control of home appliances such as cookers and heaters, flame detection, and temperature measurement. There is a demand for a highly accurate thermistor that can withstand use in a temperature range and is highly stable. Conventionally, most thermistors commonly used have operating temperatures of 250°C or less. Recently, Al ₂ O _3- based, Al ₂ O ₃ -MgO-based, and ZrO ₂ -based thermistors that can be used at higher temperatures have been developed, but the coefficient of variation (dispersion) of characteristic values such as resistance value and B constant Since the resistance is large, stable manufacturing is not possible, and the rate of change in resistance due to high-temperature current load is large, resulting in poor life characteristics. Further, manganese-zirconium thermistors are being considered as thermistors for use in the temperature range of 100 to 600°C, but they similarly have large coefficients of variation in characteristic values such as resistance and B constant during manufacture, and also have poor life characteristics. In view of the above points, the present invention has been developed at a working temperature of 100 to 600.
The present invention provides a thermistor composition that has a large B constant at ℃, a small coefficient of variation of characteristic values such as resistance value and B constant, and excellent life characteristics. The present inventors conducted various studies on manganese-zirconium based thermistors and obtained the following findings. When (1) nickel oxide is added to a mixed composition of manganese and zirconium oxides, the resistance value becomes smaller, and the coefficient of variation of characteristic values such as resistance value and B constant becomes smaller, and moreover, The resistance change rate becomes smaller. (2) Alkaline earth metals such as beryllium, calcium, magnesium, barium, and strontium; transition metals such as zinc, cobalt, chromium, iron, titanium, lanthanum, yttrium, and cerium; and aluminum, silicon, tin, lead, and bismuth. By adding one or more selected metals or their compounds, the desired resistance value can be adjusted and the B constant can be increased. The present invention was obtained based on the above findings, and contains zirconium 10 to 75 as an elemental component.
atomic%, manganese 25-85 atomic% and nickel
A thermistor composition consisting of an oxide sintered body containing 0.1 to 25 at%, and a compound mixture of 10 to 75 at% zirconium, 25 to 85 at% manganese, and 0.1 to 25 at% nickel as elemental components, beryllium, and calcium. , alkaline earth metals such as magnesium, barium, and strontium, transition metals such as zinc, cobalt, chromium, iron, titanium, lanthanum, yttrium, cerium, and metals or their compounds such as aluminum, silicon, tin, lead, and bismuth. This is a thermistor composition made of an oxide sintered body to which one or more selected from the above is added in an amount of 0.1 to 30 atomic % as an elemental component. In the present invention, 10 atomic % or less of zirconium,
The coefficient of variation of characteristic values such as resistance value and B constant is It is difficult to obtain a thermistor that is large and of stable quality, and its life characteristics are also significantly deteriorated.
However, zirconium 10-75 atom%, manganese 25-85 atom% and nickel 0.1-25 atom%
In this range, the B constant is as large as 4000K or more, the coefficient of variation of characteristic values is small, and the life characteristics are excellent. If the amount of alkaline earth metals, transition metals, and other metals added is less than 0.1 atomic %, the effect of adjusting the resistance value is small, and if it is more than 30 atomic %, the coefficient of variation of the characteristic values is large and the life characteristics are poor. However, at 0.1 to 30 atomic %, the effect of adjusting the resistance value is large and the B constant becomes large. It is unclear why the thermistor composition of the present invention has a large B constant, a small coefficient of variation of characteristic values, and excellent life characteristics. Examples of raw materials used in the present invention include zirconium such as zirconium oxide; manganese such as manganese carbonate and manganese dioxide; and nickel such as nickel oxide and nickel carbonate. Furthermore, alkaline earth metals include oxides, hydroxides, carbonates, and the like. Transition metals and other metals include metallic substances, oxides, hydroxides, carbonates, and the like. The thermistor composition according to the present invention is prepared using the above-mentioned raw materials so that it falls within a predetermined composition range, and then calcined at 900 to 1100°C, and then molded into a thermistor of a predetermined shape using this calcined product. ~1500
Obtained by firing at ℃. Thermistor shapes include bead, rod, disk, washer, and flake shapes, and the thermistor composition of the present invention is suitable for these shapes. The coefficient of variation of the resistance value of the thermistor according to the present invention is
The coefficient of variation of the B constant is 10 to 20%, and all the coefficients of variation of the B constant are 3% or less, which are extremely small and stable production is possible. Further, the thermistor composition of the present invention has a temperature of 450
The resistance change rate after 100 hours at 10 milliwatts of direct current at ℃ is less than 3%, and the resistance change rate after 1000 hours is less than 5%, and it has excellent high-temperature current load characteristics. Because of the above effects, the thermistor composition of the present invention is particularly recommended as a thermistor material used in the temperature range of 100 to 600°C. Hereinafter, the present invention will be specifically explained with reference to Examples. Example Using commercially available reagents such as special grade manganese carbonate, zirconium oxide, nickel oxide, etc., the prescribed amounts were blended to have the composition shown in Table 1, and the blended raw materials were wet-mixed for 5 hours using a ball mill (using pure water). After that, it is dehydrated and dried and calcined at 900-1100℃ for 2 hours.
Next, the calcined product is wet-pulverized (using pure water) for 3 hours using a ball mill, and then dehydrated and dried. Add about 20% dextrin solution to the above calcined powder.
%, kneaded it into a paste, and made two platinum and rhodium wires (wire diameter 60
After applying the kneaded paste in granular form on top of micron) and drying it naturally, apply 1200 m
By baking at ~1500°C for 2 hours, a bead-shaped thermistor element made of the thermistor composition of the present invention is obtained. The above bead-shaped thermistor element was spot-welded to Kovar wire, sealed in glass, and aged at 450°C for 20 hours to form a bead-shaped thermistor. For each of the bead-shaped thermistors thus obtained, the resistance values at 300 and 400°C were measured using a precision bridge resistance meter, and the B constants between these temperatures were calculated and shown in Table 2. In addition, the resistance value (at 300℃) and the coefficient of variation of the B constant when 100 thermistors are manufactured are shown in the table.
Shown in 2. Furthermore, the rate of change in resistance after 100 and 1000 hours of applying 10 milliwatts to each thermistor at 450°C (R _t - R _p /R _p × 100% R _t : resistance value after t hours, R _p : starting point) Table 2 shows the resistance value). For comparison with the thermistor of the present invention, a bead-type thermistor was prototyped using the same method using a manganese-zirconium composition that does not contain nickel, and the resistance value, B constant, and resistance change rate due to high-temperature current load were similarly measured. Also listed. As is clear from the above results, the thermistor according to the present invention was stable in production, had a large B constant, and was extremely excellent in life characteristics.

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Claims (1)

[Claims] 1. Elemental components: 10 to 75 atom% zirconium, 25 to 85 atom% manganese, and 0.1 atom% nickel.
A thermistor composition consisting of an oxide sintered body containing ~25 at.%. 2 Elemental components: 10 to 75 atom% zirconium, 25 to 85 atom% manganese, and 0.1 atomic% nickel.
~25 atomic percent of the compound mixture contains beryllium, alkaline earth metals such as calcium, magnesium, barium, strontium, transition metals such as zinc, cobalt, chromium, iron, titanium, lanthanum, yttrium, cerium, and aluminum, silicon,
A thermistor composition comprising an oxide sintered body to which 0.1 to 30 atomic % of one or more selected from metals such as tin, lead, bismuth, or compounds thereof are added as an elemental component.