JPH01253902A - Titanium acid barium semiconductor porcelain - Google Patents

Abstract

PURPOSE:To enable a semiconductor porcelain with an extreme positive resis tance temperature coefficient and a large withstand voltage by adding a specific rare-earth element to a barium titanate porcelain composition and by adding a specific amount of Mn compound and SiO2 to the base material. CONSTITUTION:By mixing barium carbonate (BaCO3), titanium oxide (TiO2), yttrium oxide (Y2O3), and calcium carbonate (CaCO3) to a specific composition, the mixed particle is tentatively calcined. A specific amount of silicon oxide (SiO2), manganese monoxide (MnO), and alumina (Al2O3) is added to the obtained tentatively sintered material and is ground and mixed in a pot. Then, a binder is added and its size-regulated powder is calcined in a natural environ ment using a circular electrical furnace formed by oil press. It allows a semicon ductor porcelain with a remarkably positive resistance temperature characteristics, a large withstand voltage, and improved reliability to be obtained.

Description

[Detailed description of the invention] (Industrial application field) This invention has a significant positive temperature coefficient of resistance.

This invention relates to barium titanate-based semiconductor porcelain that has a high withstand voltage and is highly reliable.

(Conventional technology) Conventionally, a part of Ba in barium titanate has been replaced with a trivalent element! By replacing a part of T1 with a pentavalent element and firing it in air at around 1300°C,
It is known that semiconductor porcelain having a specific resistance of 10Ωcm or less can be obtained. Barium titanate-based semiconductor ceramics obtained by adding this semiconducting agent have positive resistance-temperature characteristics, and are said to show an even greater rate of change in resistance by adding Mn. Taking advantage of this characteristic, barium titanate semiconductor ceramics are being applied to various switching elements and constant temperature heating elements for temperature control and current limiting, and have a significantly positive temperature coefficient of resistance, high withstand voltage, and high reliability. Demand for semiconductor porcelain, which has a high level of oxidation, is increasing.

(Problem to be Solved by the Invention) However, in the composition of conventional barium titanate-based semiconductor ceramics, the allowable addition range of the semiconductor agent is narrow, so variations in resistivity due to trace amounts of addition are observed, and stable ratios are not achieved. Semiconductor porcelain with resistance and difficult to produce industrially! ) In other words, in order to convert barium titanate into a semiconductor, it is necessary to add a semiconductor agent such as yttrium, but in order to keep the resistivity low, the amount added must be adjusted within a certain range. In order to obtain a practically usable specific resistance, the addition limit is limited to a fairly comfortable range.For example, in the case of yttrium, the specific resistance decreases as the amount increases up to 0.3 mol%. If it exceeds 0.3 mol%, the resistivity becomes high again, and if it exceeds 0.6 mol%, it rapidly approaches an insulator. Therefore, in order to obtain a practically possible resistivity, the amount of yttrium added should be reduced to 0.6 mol%. 1~0
．． It was necessary to set it to 6 mol%. For this reason, although it is said that the positive temperature coefficient of resistance and withstand voltage improve as the amount of semiconducting agent added increases, in the case of indium, as shown in Figure 3, specific resistance increases when 0.6 mol% or more is added. It was expensive and difficult to put into practical use.

The present invention eliminates the above-mentioned drawbacks, and achieves a practically usable low resistance in the m range of 7111 added with a semiconducting agent, which was conventionally said to become an insulator, and has a remarkable positive temperature coefficient of resistance. The present invention provides a barium titanate-based semiconductor porcelain having a high withstand voltage and high reliability.

(Means for Solving the Problems) The present invention provides a barium titanate-based semiconductor ceramic composition or B
1.0 to 1.5 mol % of Y based on the barium titanate ceramic composition in which a part of a is replaced with Ca''C.

At least one of Sb, Bi, Ta, Nb, and rare earth elements is added, and 0.1 Mn compound is added to 100 mol of this base material.
By adding ~0.2 mol and 0.5 to 5 mol of SiO2, it is possible to obtain a barium titanate-based semiconductor porcelain that has remarkable positive resistance-temperature characteristics, high withstand voltage, and high reliability.

(Actions and Examples) The present invention will be explained below with reference to Examples.

Barium carbonate (BaCO,), titanium oxide (Ti02)
, yttrium oxide (Y 20 s ) and calcium carbonate (Ca COs ) were blended to have the composition shown in Table 1, placed in a polyethylene pot together with an agate ball, and mixed for 20 hours.The mixed powder was 950-11
Temporary firing was performed at 00°C for about 15 hours. Silicon oxide (SiO3), -manganese oxide (MnO), and alumina (Alx's) were added to the obtained calcined raw material as shown in Table 1, and the mixture was ground for 20 hours using an agate ball in a polyethylene pot. After mixing, a polyvinyl alcohol aqueous solution was added as a binder, and the particles were sized using a 30-mesh sieve.
It was molded into a 20φ×31 mm disc under a pressure of g/cm′. This shaped disk was fired in an electric furnace at a temperature of 1250 to 1300° C. for about 1.5 hours tWI in a natural atmosphere. Ag paste was baked on both sides of the sample thus obtained, ti of ohmic contact was provided, and this was used as a sample.

For these samples, the specific resistance at room temperature (25°C),
The temperature coefficient of resistance and withstand voltage characteristics were measured and the values are shown in Tables 2 and 3.

Among the above-mentioned various characteristics, the temperature coefficient of resistance indicates the slope of the rise after a sudden resistance change point in the resistance temperature characteristics, and is defined as follows.

T t T + Here, R2 and R1 are resistance values at two arbitrary points on a straight line that suddenly rises beyond a sudden resistance change point in the resistance temperature characteristic. Further, T and T2 are the respective temperatures at 1[1 and R2. Further, the withstand voltage characteristic is a value that indicates the maximum applied voltage value before the sample breaks down when a voltage is gradually applied to the sample. In addition, Table 1, Table 2
In Tables and Table 3, the sample numbers marked with an O are within the scope of this invention, and all others are outside the scope of the invention.

(Effect of the invention) According to the above examples, sample number 1 falls within the scope of this invention.
It can be seen that samples 2 to 24.30 to 33.35 to 44 have large positive temperature coefficients of resistance and excellent withstand voltage characteristics.

This situation is shown in FIGS. 1 and 2 by extracting sample number 22, which is within the scope of the present invention, and sample number 5, which is outside the scope of the invention.

Figure 1 shows the resistance temperature characteristics, and sample number 5
The temperature coefficient of resistance is as low as 20.4%/°C, while that of sample number 22 within the scope of the present invention is 52.8%/°C.
%/°C, and it can be seen that the rise in the figure is steep. Figure 2 shows the voltage-current characteristics.
In sample number 5, the current value becomes L j4 when it exceeds 300V.
At first, if the voltage is increased further, the element will be destroyed, but in sample number 22, which falls within the scope of the present invention, the current value decreases linearly when the voltage is increased to 500 V, indicating that the withstand voltage is high. There is.

In the present invention, the addition range of the semiconducting agent is set to 10 to 15 mol % because violet has traditionally been added when less than 10 mol % is added. Even if you change sample number 1~
As seen in Sample No. 10, the positive temperature coefficient of resistance and withstand voltage characteristics are small, and no effect sufficient to meet the purpose of the present invention can be obtained. This is because it becomes expensive.

Furthermore, the addition range of the Mn compound was set to 0.01 to 0.2 moles per 100 moles of the base material to which the semiconducting agent was added.
When less than 1 mole is added, the resistivity is high as in sample number 11, and even when more than 0.2 mole is added, sample number 25
This is because the specific resistance becomes high as seen in .

The reason why the addition range of Sin was set to 05 to 5 mol per 100 mol of the base material to which the semiconducting agent was added was because if less than 0.5 mol was added, as seen in sample numbers 28 and 29, the specific resistance If more than 5 mol is added, the specific resistance will become high as in sample number 34, and the positive temperature coefficient of resistance and withstand voltage characteristics will become smaller.

In addition, as shown in sample numbers 38 to 44 in the examples, barium titanate ceramic compositions were added with a semiconducting agent, a Mn compound, and SiO□ within the scope of the present invention.
Even for those in which part of was replaced with Ca, a material with a large resistance temperature coefficient and excellent withstand voltage characteristics was obtained.

Furthermore, Al2, which is generally said to improve reliability tests,
Even when O> was added to a composition within the scope of the present invention, samples with a large positive temperature coefficient of resistance and excellent withstand voltage characteristics were obtained, such as sample numbers 35 to 37.43.44. .

In addition, the device in the example was tested at 125V at a high temperature of 85°C.
After applying a voltage of 1000 ± 12 hours, it was taken out at room temperature, left for 1 hour, and the resistance value at room temperature was measured.
．． 30-33. All 35-44 have a resistance change rate of 10%.
A highly reliable result was obtained within

As described above, in the region where the amount of semiconductor forming agent added is too large and the specific resistance suddenly approaches that of an insulator, Mn (arsenic compound, 5t02) is added in the amount specified in the present invention, and 1250
By firing at a temperature of ~1300°C, for practical purposes,
As a result, the variation in resistivity caused by the addition of the semiconductor 1st agent is reduced, and it also has a high withstand voltage with a remarkable positive resistance temperature characteristic and is reliable. It is now possible to obtain a barium titanate-based device with high properties.

Furthermore, although indolium was used as the semiconductor agent in the embodiments of the present invention, similar effects can be obtained with other semiconductor elements. Furthermore, the barium titanate-based porcelain composition of the present invention contains P b , S
Also included are those containing r, S Ll, Z r, etc.

(Margin below) No. 271

[Brief explanation of the drawing]

FIG. 1 is a resistance-temperature characteristic diagram of a barium titanate semiconductor ceramic according to an embodiment of the present invention, and FIG. 2 is a voltage-current characteristic diagram thereof. Sample number 22 in each characteristic diagram
is within the scope of this invention, and sample number 5 is outside the scope. FIG. 3 is a characteristic diagram showing the relationship between the amount of yttrium added and the specific resistance of barium titanate-based semiconductor ceramics.

Claims (1)

[Claims] 1.0 to barium titanate ceramic composition or barium titanate ceramic composition in which a part of Ba is replaced with Ca.
Add 1.5 mol% of Y, Sb, Bi, Ta, Nb, and at least one of rare earth elements, and add 0.1 to 0.2 mol of Mn compound and 0.5 mol of SiO_2 to 100 mol of this base material.
Barium titanate-based semiconductor porcelain constituted by adding ~5 mol of barium titanate.