JPH04338601A - Semiconductor porcelain having positive resistance temperature coefficient and manufacture thereof - Google Patents

Abstract

PURPOSE:To improve the static breakdown strength of a barium titanate semiconductor porcelain having a positive resistance temperature coefficient. CONSTITUTION:The ratio In/Is of the X-ray diffractive strength In of the Ba2 TiSizO8(1,1,1) face at the center of a barium titanate semiconductor porcelain baked substance to the X-ray diffractive strength Is of the Ba2TiSiO2O8(1,1,1) face at the surface of that semiconductor porcelain baked substance is made 7 or more. For that purpose, the mixed material where Ba2TiSi2O8 is added to the barium titanate semiconductor material is smashed so that the average diameter may be 3mum or less and then it is baked.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barium titanate (BaTiO3) based semiconductor ceramic having a positive temperature coefficient of resistance, and more particularly to a semiconductor ceramic having a high static withstand voltage and a method for manufacturing the same.

0002

[Prior Art] In recent years, barium titanate (BaTiO3)-based semiconductor porcelain has been developed which has a large positive temperature coefficient of resistance. Because it reduces the amount of current generated, it is widely used for various purposes such as overcurrent protection in circuits and degaussing of cathode ray tube frames in television receivers. On the other hand, in order to improve the reliability of devices using barium titanate-based semiconductor ceramics, there is an increasing demand for semiconductor ceramics that have a higher static withstand voltage and a positive temperature coefficient of resistance.

Conventionally, as a method for improving the static breakdown voltage of barium titanate-based semiconductor ceramics, Ba
A method has been proposed in which a component material having an average composition of Ba2TiSi2O8 is added to a TiO3-based material and fired (Japanese Patent Application Laid-open No. 296401/1983).

0004

[Problems to be Solved by the Invention] However, although the above conventional methods can improve the static withstand voltage of semiconductor ceramics to some extent, the problem is that the effect is not necessarily sufficient. There is a need for porcelain and methods for making the same.

The present invention solves the above-mentioned problems, and aims to provide a semiconductor porcelain having a positive temperature coefficient of resistance that is superior in static withstand voltage than conventional semiconductor porcelain, and a method for manufacturing the same.

[0006]

[Means for Solving the Problems] In order to achieve the above object, the semiconductor porcelain having a positive temperature coefficient of resistance of the present invention has a barium titanate based semiconductor material with Ba2TiSi2O.
barium titanate-based semiconductor porcelain having a positive temperature coefficient of resistance that is fired with the addition of Ba2 on the surface of the semiconductor porcelain fired body
It is characterized in that the ratio In/Is to the X-ray diffraction intensity Is of the TiSi2O8 (1,1,1) plane is 7 or more.

[0007] Furthermore, the method of manufacturing semiconductor porcelain having a positive temperature coefficient of resistance according to the present invention involves pulverizing a mixed material in which Ba2TiSi2O8 is added to a barium titanate-based semiconductor material until the average particle size becomes 3 μm or less. It is characterized by being fired.

The inventors conducted intensive studies to further improve the static breakdown voltage of semiconductor ceramics having a positive temperature coefficient of resistance, and added Fresnite (B) to BaTiO3-based semiconductor ceramic materials.
It was discovered that the distribution state of Ba2TiSi2O8 in a semiconductor porcelain fired body which is fired with the addition of a2TiSi2O8) has an important relationship with the static withstand voltage, and the present invention was completed. That is, in the semiconductor porcelain of the present invention, B
Ba2TiSi for calcined powder of aTiO3-based semiconductor ceramic material
By adding 2O8, pulverizing it until the average particle size becomes 3 μm or less, and then firing it, the distribution density of Ba2TiSi2O8 in the center of the fired body (semiconductor porcelain) becomes higher than that in the surface area, and the static withstand pressure increases. improves. Then, Ba in the center of the semiconductor porcelain fired body obtained as described above is
X-ray diffraction intensity In of 2TiSi2O8 (1,1,1) plane
and Ba2TiSi2O on the surface of the semiconductor porcelain fired body.
8(1,1,1) plane X-ray diffraction intensity Is ratio In/I
s becomes 7 or more.

[0009]

EXAMPLES The features of the present invention will be explained in more detail by way of examples.

[0010] BaCO3, TiO2, Y2O3, CaC
O3 and Mn2O3 are mixed to have a composition expressed by the following formula (1). (Ba0.896Ca0.10Y0.004)Ti
O3+0.0005Mn...(1) Then, this was placed in a polyethylene pot with pure water and zirconia balls, pulverized and mixed for 5 hours, dried, and
Calcinate at ℃ for 2 hours. This calcined powder contains 1 mol% Ba2T.
A mixed material having the composition of formula (2) below is prepared by adding iSi2O8. [(Ba0.896Ca0.10Y0.004)TiO
3+0.0005Mn]+0.01Ba2TiSi2O
8

...(2)

[0011] This is placed in a polyethylene pot, and a binder is added thereto, as well as zirconia balls and pure water, followed by pulverization and mixing. This results in
The distribution of Ba2TiSi2O8 is controlled by changing the average particle size of the mixed material in the range of 0.5 to 5 μm. after that,
This slurry is dried and granulated, and a disk-shaped molded body with a diameter of 17 mm and a thickness of 1 mm is produced using a press molding machine. Then, this molded body was heated at 1350°C at a rate of 8°C/min.
, bake at that temperature for 30 minutes, and then heat to 8℃.
A fired body (semiconductor porcelain) was produced by cooling to room temperature at a rate of /min. Then, an electrode material was applied to both main surfaces of this semiconductor ceramic to form electrodes, and a sample was prepared for characteristic measurement.

Table 1 shows B for the samples of the above examples.
The average particle size of the mixed material after mixing and pulverizing a2TiSi2O8, Ba2TiSi2O8 (1
, 1, 1) X-ray diffraction intensity In of the plane and Ba2Ti of the surface part
Ratio I of X-ray diffraction intensity Is of Si2O8 (1,1,1) plane
n/Is, resistance at room temperature (25°C), and static breakdown voltage (
The voltage value at which the current reaches its minimum value when the voltage applied to the element is increased is shown.

[0013]

[Table 1]

[0014] In Table 1, the samples marked with * are outside the scope of the present invention. From Table 1, by setting the average particle size of the mixed material to 3 μm or less, the value of the X-ray diffraction intensity ratio In/Is between the center and surface area becomes 7 or more, and when the average particle size becomes 0.5 μm, In The value of /Is is 36. Furthermore, when the value of the X-ray diffraction intensity ratio In/Is becomes 7 or more (that is, the average grain size of the mixed material is 3 μm or less), the static withstand voltage of the semiconductor porcelain exceeds 70 V, which indicates a significant improvement. . In addition, even if In/Is becomes larger than that, the static withstand voltage will not improve so rapidly,
81 when In/Is is 36 (average particle size 0.5 μm)
It is V. Therefore, the X-ray diffraction intensity ratio In/I
It is preferable that s be 7 or more.

On the other hand, the specific resistance is almost constant (0.83 to 0.87Ω) regardless of the average particle size of the mixed material.
It can be seen that this is not affected by the average particle size of the mixed material (ie, the value of In/Is).

The barium titanate-based semiconductor material, which is the main component of the semiconductor porcelain having a positive temperature coefficient of resistance according to the manufacturing method of the present invention, may be partially substituted with Ca or the like, or may be made of a semiconductor material. Various barium titanate-based materials containing rare earth elements such as Y or elements such as Nb and Sb can be used as the curing agent.

[0017]

Effects of the Invention As described above, the semiconductor ceramic having a positive temperature coefficient of resistance of the present invention has a Ba
Since the ratio In/Is of the X-ray diffraction intensity of 2TiSi2O8 is set to be 7 or more, the static breakdown voltage can be improved while maintaining the low resistance of the ceramic.

[0018] Furthermore, the method for manufacturing semiconductor porcelain having a positive temperature coefficient of resistance according to the present invention includes adjusting the particle size of the mixed material obtained by mixing BaTiO3-based semiconductor material with Ba2TiSi2O8 and pulverizing the mixture so that the average particle size is 3 μm or less. Since this is fired, it is possible to control the distribution of Ba2TiSi2O8 so that the above-mentioned X-ray diffraction intensity ratio In/Is is 7 or more, resulting in a positive resistance with excellent static pressure resistance. A semiconductor porcelain having a temperature coefficient can be obtained.

Claims (2)

[Claims] [Claim 1] Ba is added to the barium titanate-based semiconductor material.
A barium titanate-based semiconductor porcelain having a positive temperature coefficient of resistance that has been fired with the addition of 2TiSi2O8, the Ba2TiSi2O8 (1,1
, 1) The ratio In/Is of the X-ray diffraction intensity In of the plane to the X-ray diffraction intensity Is of the Ba2TiSi2O8 (1,1,1) plane of the surface portion of the semiconductor ceramic fired body is 7 or more. Semiconductor porcelain with a positive temperature coefficient of resistance. [Claim 2] Ba is added to the barium titanate-based semiconductor material.
The average particle size of the mixed material added with 2TiSi2O8 is 3μ.
2. The method of manufacturing semiconductor porcelain having a positive temperature coefficient of resistance according to claim 1, further comprising pulverizing the porcelain until it becomes less than m and firing the porcelain.