JP3166787B2 - Barium titanate-based semiconductor porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION This invention relates to a semiconductor ceramic composition, particularly to a positive barium titanate having a resistance-temperature characteristic (BaTiO ₃₎ based semiconductor ceramic composition.

[0002]

2. Description of the Related Art In recent years, barium titanate (BaTiO ₃ ) -based semiconductor ceramic compositions having a large positive resistance temperature characteristic have been developed. The barium titanate-based semiconductor porcelain composition has a resistance value that rapidly increases when the Curie temperature is exceeded, and reduces the amount of current passing therethrough. It is widely used for various purposes such as degaussing.

[0003]

However, the conventional barium titanate-based semiconductor porcelain composition has a positive resistance temperature characteristic in a temperature range in which the crystal structure is cubic, but it has a lower temperature. On the other hand, in the temperature range where the crystal structure is tetragonal, it has a negative resistance-temperature characteristic. Therefore, it is extremely difficult to formulate the resistance temperature characteristic over the entire temperature range from the tetragonal temperature range to the cubic temperature range. For example, a positive temperature coefficient thermistor made of a barium titanate-based semiconductor ceramic composition However, there is a problem that it is impossible to theoretically accurately and efficiently design a circuit using, and its use is restricted.

An object of the present invention is to provide a barium titanate-based semiconductor ceramic composition having a positive resistance temperature characteristic even in a tetragonal crystal temperature range. I do.

[0005]

In order to achieve the above object, the barium titanate-based semiconductor ceramic composition of the present invention has a temperature range in which the crystal structure is tetragonal and a cubic crystal structure. In both temperature ranges of the temperature range,
Have a positive resistance temperature characteristic, the general _{formula: (Ba 1-vw Sr v} Me w) TiO 3 + yMn + zSiO 2 ( where, Me is Y, La, rare earth elements such as Ce, N
selected from the group consisting of b, Bi, Sb, W, Th and Ta
Is represented by the at least one), v, w, z are each in the range of 0.01 ≦ v ≦ 0.4 0.0003 ≦ w ≦ 0.0029 0.001 ≦ z ≦ 0.04, and , W in the range of 0.6 ≦ y / w ≦ 4 .

[0006]

[0007]

EXAMPLES The features of the present invention will be described in more detail with reference to Examples of the present invention and Comparative Examples.

(Example 1) General formula: (Ba _0.88-W Sr _0.12 Me _w ) TiO ₃ +0.
To produce a barium titanate-based semiconductor ceramic composition represented by 001Mn + 0.02SiO _2, it was examined their resistance-temperature characteristic.

Here, Me is La, Ce, Pr, Nd,
It is at least one of Sm, Cd, Ho, Dy, Y, and Er.

In producing the barium titanate-based semiconductor porcelain composition, first, the raw materials BaCO _3,
SrCO ₃ , La ₂ O ₃ , Ce ₂ O ₃ , Pr ₂ O ₃ , N
_{d 2 O 3, Sm 2 O} 3, Cd 2 O 3, HoO, Dy 2 O
₃ , Y ₂ O ₃ , Er ₂ O ₃ , TiO ₂ , MnCO ₃ , S
iO ₂ is blended at a predetermined ratio so as to have the composition shown in Table 1.

Next, this compounded raw material is wet-mixed in a pot mill for 5 hours, dehydrated and dried, and then calcined at 1150 ° C. for 2 hours. Then, the obtained calcined raw material was pulverized, mixed with vinyl acetate as a binder, granulated, and then formed into a square plate having a long side of 12 mm, a short side of 7 mm, and a thickness of 4 mm by a dry press to prepare a sample. . Then, this sample is placed in an air atmosphere for 1 hour.
Sintering was performed under a temperature condition of 300 to 1370 ° C. to obtain a semiconductor ceramic (a barium titanate-based semiconductor ceramic).

[0012] Then, on both sides of the obtained semiconductor porcelain, I
An electrode was formed by applying an n-Ga alloy, and the specific resistance (ρ) and the temperature coefficient of resistance at normal temperature were measured. Table 1 shows the results.
Shown in

[0013]

[Table 1]

The temperature coefficient of resistance in Table 1 was obtained by the method described below.

FIG. 1 is a diagram showing an example of the resistance-temperature characteristics of a barium titanate-based semiconductor ceramic (composition) according to an embodiment of the present invention. In the barium titanate-based semiconductor porcelain having such characteristics, the resistance temperature coefficient of the region a in FIG. 1 (a temperature range in which the crystal structure is a tetragonal system) is A (% /
C), and the temperature coefficient of resistance in the region b (temperature range in which the crystal structure is a cubic system) is B (% / ° C.), and A and B are represented by the following equations: A, B = ｛(2.303 La log R ₂ / R ₁ ) / (T ₂ −
T ₁ )｝ × 100 (% / ° C.) (however, T ₁ <T ₂ ) T ₁ : arbitrary temperature in region a T ₂ : arbitrary temperature in region b R ₁ : resistance value at T ₁ R ₂ : determined by the resistance value of _{T 2.}

Here, when the values of A and B are A, B> 0, when the resistance temperature characteristics are positive characteristics A, B = 0, when the resistance temperature characteristics are flat characteristics A, B <0, Indicates that the resistance-temperature characteristic is a negative characteristic.

In Table 1, those marked with * are the comparative examples outside the composition range described in claim 2, and the others are examples within the composition range described in claim 2. .

As shown in Table 1, in the barium titanate-based semiconductor porcelain according to the embodiment of the present invention, A> 0 for all types of Me, and the crystal structure is positive in a tetragonal temperature range. It can be seen that a barium titanate-based semiconductor porcelain having the resistance-temperature characteristics described above has been obtained. Further, in claim 2, the range of the addition amount w of Me is defined as w <
The reason for limiting to 0.0029 is that when the addition amount w is 0.0029 as in sample numbers 5 and 11, there is Me in which the resistance temperature characteristic becomes flat in the tetragonal temperature range. .

Example 2 General formula: (Ba _0.88-w Sr _0.12 Me _w ) TiO ₃ + y
A barium titanate-based semiconductor ceramic composition represented by Mn + 0.02SiO ₂ was manufactured under the same conditions as in Example 1 described above, and the influence of the content ratio of Me and Mn was examined.

Table 2 shows the relationship between the contents of Me and Mn, the specific resistance (ρ) at room temperature, and the temperature coefficient of resistance, which were examined for the semiconductor ceramic of this embodiment.

[0021]

[Table 2]

In Table 2, those with * added to the sample numbers are comparative examples of compositions outside the scope of the present invention, and the others are examples of compositions within the scope of the present invention. As shown in Table 2, in comparative examples outside the scope of the present invention, A ≦ 0 ,
Alternatively, even if A> 0 as in sample number 13, A is 0
It has become near, while the resistance-temperature characteristic is substantially flat or negative characteristics, in the barium titanate type semiconducting ceramic according to an embodiment of the present invention, the content ratio of Me and Mn as shown in Table 2 A> 0, it can be seen that the crystal structure has a positive resistance temperature characteristic in a tetragonal temperature range.

Further, with respect to the contents of Sr and SiO ₂ , the resistance-temperature characteristics can be controlled to some extent by appropriately adjusting the contents within the scope of the present invention. FIG. 2 shows the resistance-temperature characteristics of two types of barium titanate-based semiconductor porcelain in which the Curie point was shifted by changing the content ratio of Sr, and in each case, the crystal structure was within a tetragonal temperature range. It can be seen that it has a positive resistance-temperature characteristic.

[0024]

According to the present invention as described above, barium titanate-based semiconductor ceramic composition of the present invention, Rutotomo to have a positive resistance-temperature characteristics in the temperature range crystal structure is tetragonal
In addition, since the crystal structure is made to have a positive resistance temperature characteristic even in the temperature range where the crystal structure is cubic, the resistance temperature characteristic is maintained over the entire temperature range from the tetragonal temperature range to the cubic temperature range. Can be easily and accurately formed into a mathematical expression, and a circuit using a positive temperature coefficient thermistor or the like can be theoretically, accurately, and efficiently designed.

In addition, the general formula: (Ba_1-V-WSr_VMe_W) TiO₃ + YMn+ Z
SiO₂  Combine each component so that it has the composition represented by
In the temperature range where the crystal structure is tetragonal,
Barium titanate based semiconductor with positive resistance temperature characteristics
The porcelain composition can be reliably obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing resistance temperature characteristics of a barium titanate-based semiconductor ceramic composition according to an example of the present invention.

FIG. 2 is a diagram showing resistance temperature characteristics of a barium titanate-based semiconductor ceramic composition according to another embodiment of the present invention.

[Explanation of symbols]

 a Temperature range where the crystal structure is tetragonal b Temperature range where the crystal structure is cubic

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Claims (1)

(57) [Claims] 1. A temperature range in which the crystal structure is tetragonal,
Temperature range crystal structure is a cubic system, in both temperature ranges, have a positive resistance-temperature characteristics, the general _{formula: (Ba 1-vw Sr v} Me w) TiO 3 + yMn + zSiO 2 ( where, Me is Y , La, Ce and other rare earth elements, N
selected from the group consisting of b, Bi, Sb, W, Th and Ta
Is represented by the at least one), v, w, z are each in the range of 0.01 ≦ v ≦ 0.4 0.0003 ≦ w ≦ 0.0029 0.001 ≦ z ≦ 0.04, and , A ratio of y to w is in the range of 0.6 ≦ y / w ≦ 4 .