JP2882131B2 - Method for manufacturing oxide semiconductor for thermistor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermistor oxide semiconductor having a negative temperature coefficient of resistance, which is used as a temperature sensor for medium and high temperatures in a temperature range of -60.degree.

[0002]

2. Description of the Related Art In general, this type of oxide semiconductor for a thermistor contains a Mn-Ni-Cr-based oxide as a main component,
A material obtained by adding a small amount of Si or Al having a function of controlling the resistance value is used. First, the manufacturing method
Predetermined amounts of the oxides of the above-mentioned various metal elements as raw materials are weighed, and they are put into a ball mill and mixed. Further, a binder is added to the mixture and the mixture is molded, and the molded body is fired to produce an oxide semiconductor for a thermistor.

[0003]

However, in the conventional manufacturing method, silicon oxide produced by a wet method of neutralizing sodium silicate with an acid is used as a raw material silicon oxide. Since silicon has properties such as low bulk density, easy aggregation, and hardness and pulverization, it cannot be uniformly dispersed by short-time mixing, and requires long-time mixing. In addition, since it is difficult to uniformly disperse silicon oxide, there is also a problem that characteristics such as specific resistance of the oxide semiconductor for a thermistor after firing are largely varied.

An object of the present invention is to solve the above-mentioned conventional problems, and it is an object of the present invention to facilitate the uniform dispersion of silicon oxide, thereby shortening the mixing time and reducing the variation in characteristics.

[0005]

In order to achieve this object, a method of manufacturing an oxide semiconductor for a thermistor according to the present invention is manufactured by a melting method in which silica is melted in silicon oxide used as a raw material, and then cooled and ground. In this case, silicon oxide is used.

[0006]

The silicon oxide produced by this melting method is
Since the bulk density is higher than that of conventional general silicon oxide, and it has properties such as being less likely to aggregate, it can be easily and uniformly dispersed by mixing in a short time. Further, since the silicon oxide having a function of controlling the resistance value is uniformly dispersed, the variation in the specific resistance of the baked oxide semiconductor for a thermistor becomes extremely small.

[0007]

An embodiment of the present invention will be described below. First, manganese carbonate, nickel oxide, chromium oxide, and silica were melted so as to have the composition of A or B shown in the composition table of the oxide semiconductor for thermistor in Table 1 and then manufactured by a melting method of cooling and pulverizing. Silicon oxide (for example, product number FS-20, manufactured by Denki Kagaku Kogyo KK) was weighed, placed in a ball mill, and wet-mixed for 5 hours.

[0008]

[Table 1]

Next, after drying the mixture, polyvinyl alcohol was added and mixed as a binder, and the mixture was molded to produce a disk-shaped molded body having a diameter of 12 mm and a thickness of 2 mm.

Further, the molded body was fired in air at 1300 ° C. for 2 hours to obtain an oxide semiconductor for a thermistor. A silver electrode was provided on the obtained disk-shaped oxide semiconductor to obtain a sample for measuring characteristics.

As a comparative example, a sample was prepared under the same manufacturing conditions as in the above example using silicon oxide manufactured by a conventional wet method (a method of neutralizing sodium silicate with an acid). As another example, a sample in which wet mixing was performed for 16 hours using a ball mill was also manufactured. Then, for each of these many samples of the examples, comparative examples and conventional examples, 2
The specific resistance at 5 ° C. and the thermistor constant (B constant) at 25 ° C. and 50 ° C. were measured, and the average value was obtained from the measured values.

[0012]

[Outside 1]

The standard deviation σ and the coefficient of variation

[0014]

[2] σ /

Was calculated. The calculation results are shown in Table 2 for specific resistance and Table 3 for thermistor constant.
Are shown below.

[0016]

[Table 2]

[0017]

[Table 3]

As is clear from Tables 2 and 3, the mixing time of the sample of this example using silicon oxide as a raw material by the melting method is reduced to 1/3 or less of that of the conventional example. Nevertheless, the σ value, which indicates the degree of variation in specific resistance and thermistor constant,

[0019]

[Outside 3] σ /

The value is equal to or smaller than that of the conventional example, and the degree of variation in characteristics is improved. In particular, the σ value of the specific resistance and

[0021]

[Outside 4] σ /

The value of this embodiment is as small as approximately half that of the conventional example, and the variation of the specific resistance is greatly reduced by the manufacturing method of this embodiment. The specific resistance and thermistor constant

[0023]

[Outside 5]

The values are almost the same as those of the conventional example, and a value of a predetermined standard value can be obtained. On the other hand, in the case where the mixing time was shortened by using silicon oxide by the wet method as a raw material, as can be seen from the results of the comparative examples, the values of the specific resistance and the thermistor constant were obtained at predetermined standard values, although σ Value and

[0025]

[6] σ /

The values are quite large and vary widely, and it is extremely difficult to shorten the mixing time by using raw materials by a wet method.

As described above, the mixing time can be greatly reduced by using the silicon oxide raw material by the melting method, and the variation in the specific resistance is significantly reduced. Since the bulk density is higher than that of the material and it is hard to aggregate, the silicon oxide is easily and uniformly dispersed by mixing in a short time. Therefore, since the dispersibility of the silicon oxide that functions to control the resistance value is excellent, the variation in the specific resistance of the baked oxide semiconductor for thermistor can be suppressed to an extremely small value.

[0028]

As is apparent from the above description, the present invention uses silicon oxide produced by a melting method for silicon oxide used as a raw material, thereby significantly shortening the mixing time and achieving high precision with small characteristic variations. A simple manufacturing method capable of obtaining a good oxide semiconductor for a thermistor can be realized.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-264854 (JP, A) JP-A-60-106107 (JP, A) JP-A-59-208804 (JP, A) JP-A-57-208 64903 (JP, A) JP-A-57-15403 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H01C 7/02-7/22

Claims (1)

(57) [Claims] 1. A method for producing a thermistor oxide semiconductor containing oxides of manganese, nickel, chromium and silicon, wherein silicon oxide produced by a melting method in which silica is melted, and then cooled and pulverized. A method for manufacturing an oxide semiconductor for a thermistor, which is used.