JPH04280861A - Composition for barium titanate-based semiconductor porcelain and barium titanate-based semiconductor porcelain using the same composition - Google Patents

Abstract

PURPOSE:To provide the subject barium titanate-based semiconductor porcelain having a positive temperature characteristics of resistance in a high temperature region of >=200 deg.C, maintaining the initial practical specific resistance value at ordinary temperatures, having a fine crystal structure, showing a high maximum voltage per unit thickness and suitable for a constant temperature heater and to provide the subject composition for production thereof. CONSTITUTION:A composition obtained by blending 100mol TiO2 with 50-80mol BaCO3m 20-40mol PbO 3-8mol CaCO3, 2-9mol SrCO3, 0.10-0.16mol Nb2O5, 0.03-0.07mol MnCO3, 2.0-3.0mol SiO2 and 0.05-1.0mol Al2O3 and a semiconductor porcelain produced by wet-pulverization blending the above-mentioned composition, and after dehydration and drying, calcining it at 1000-1100 deg.C, subjecting to repeating wet-pulverization blending, dehydration and drying, subsequently mixing a binder therewith, molding the resultant mixture and sintering the molded material at 1250-1300 deg.C for 0.5-3hr.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barium titanate semiconductor ceramic composition and a barium titanate semiconductor ceramic composition obtained using the composition.

0002

[Prior Art] Conventionally, for example, Japanese Patent Publication No. 63-28324
The publication contains BaTiO3 and CaTiO as main components.
No. 3, a barium titanate-based semiconductor ceramic composition comprising SrTiO3 and PbTiO3, a rare earth element as a semiconductor agent, and Mn and SiO2 as additives is disclosed.

[0003] Furthermore, JP-A No. 58-68903 discloses that BaCO3, PbO, CaCO3 as main raw materials
, SrCO3 and TiO2, Y2 O3 as a semiconducting agent, MnCO3 as an additive, SiO2
A barium titanate-based semiconductor ceramic made by adding Al2O3 and Al2O3 is disclosed.

[0004] Japanese Patent Publication No. 55-42442 discloses that Nb is added as a semiconductor element to barium titanate or a barium titanate solid solution in which a part of the barium is replaced with tin or lead, and further Mn and SiO2 are added. A barium titanate-based semiconductor ceramic material is disclosed.

[0005]

[Problem to be Solved by the Invention] When barium titanate-based semiconductor ceramics is used as a semiconductor with positive resistance-temperature characteristics in a constant-temperature heating element, etc., what is the maximum usage that can maintain its positive resistance-temperature characteristics? Make sure the voltage is high enough
This is important from a safety point of view. Furthermore, barium titanate-based semiconductor porcelain having a higher maximum operating voltage at which it can maintain its positive resistance-temperature characteristics can be used in a wider range of applications as electrical components.

When an electrode is attached to barium titanate-based semiconductor porcelain and an alternating current voltage is gradually applied to it, the voltage at which the electrical resistance value reaches its maximum is the maximum voltage that can maintain positive resistance-temperature characteristics. This is the voltage used. The value obtained by dividing the effective value of this maximum AC voltage (Vrms) by the thickness (mm) of the barium titanate-based semiconductor porcelain sandwiching the electrodes [hereinafter referred to as the maximum working voltage per unit thickness (Vrms/mm)] is larger for titanium. The barium oxide semiconductor porcelain makes it possible to obtain smaller and safer products.

[0007] In barium titanate semiconductor ceramics according to the prior art, the maximum operating voltage per unit thickness was not sufficiently high. One of the reasons for this is that the crystal structure of barium titanate-based semiconductor ceramics produced by conventional techniques is not sufficiently fine. On the other hand, if the crystal structure of the semiconductor ceramic becomes too fine, the resistance per unit thickness will increase, making it impossible to achieve the intended purpose.

[0008] The present inventors have conducted various studies on barium titanate-based semiconductor ceramic compositions and barium titanate-based semiconductor ceramics obtained using the compositions in order to solve the problems remaining in the prior art. By using a barium titanate-based semiconductor porcelain composition obtained by specifying each component of the main raw material, semiconducting agent, and additive, and specifying the blending ratio of each component, its practical room-temperature specific resistance We have succeeded in obtaining a barium titanate-based semiconductor device whose crystal structure is sufficiently fine and whose maximum operating voltage per unit thickness has been significantly increased while maintaining the desired value, and we are now proposing this. It is something.

The present invention has a significantly positive resistance-temperature characteristic in a high temperature region of 200° C. or higher, maintains the desired practical specific resistance value at room temperature, and has a sufficiently fine crystal structure to form a unit The object of the present invention is to provide barium titanate-based semiconductor porcelain having a high maximum operating voltage per thickness, and a composition for barium titanate-based semiconductor porcelain used in its production.

Another object of the present invention is to provide a barium titanate-based semiconductor porcelain mainly used as a constant-temperature heating element, and a barium titanate-based semiconductor porcelain composition used for the production thereof.

[0011]

[Means for solving the problems] That is, the present invention has the following features:
BaCO3, PbO, CaCO3 as main raw materials,
SrCO3 and TiO2, N as a semiconducting agent
b2 O5, MnCO3 as additive, SiO2
A barium titanate-based semiconductor ceramic composition comprising: .10-0.16 mol, MnCO3
0.03-0.07 mol, SiO2 2.0-3.0
The above-mentioned barium titanate-based semiconductor porcelain composition comprising 0.05 to 1.0 mol of Al2O3 and the barium titanate-based semiconductor porcelain composition are wet-pulverized and mixed, and after dehydration and drying. , 1000-11
Calcined at a temperature of 00°C, wet pulverized and mixed again, dehydrated and
After drying, mix binder and mold, 1250~130
The present invention provides barium titanate-based semiconductor porcelain obtained by sintering at a temperature of 0° C. for 0.5 to 3 hours.

The barium titanate-based semiconductor ceramic composition of the present invention contains BaCO3, PbO, Ca as main raw materials.
CO3, SrCO3 and TiO2, Nb2O5 as a semiconducting agent, MnCO3 as an additive
, SiO2 and Al2O3 in a predetermined ratio.

The amounts of each of the main raw materials, semiconducting agents and additives to be used will be explained below.

The amount of BaCO3 used as the main raw material is usually 50 to 80 moles per 100 moles of TiO2. If the amount used is less than 50 moles, it will be difficult to make it into a semiconductor, and if it exceeds 80 moles, it will be impossible to obtain a switching temperature of 200° C. or higher.

The amount of PbO used as the main raw material is usually 20 to 40 moles per 100 moles of the TiO2. If the amount of PbO used is less than 20 moles, 200 moles
It is not possible to obtain a switching temperature of .degree. C. or higher, and if the amount exceeds 40 mol, it becomes difficult to make a semiconductor.

The amount of CaCO3 used as the main raw material is usually 3 to 8 moles per 100 moles of TiO2. If the amount of CaCO3 used is less than 3 moles,
The maximum working voltage becomes low, and if it exceeds 8 mol, it becomes difficult to make it into a semiconductor.

The amount of SrCO3 used as the main raw material is usually 2 to 9 moles per 100 moles of TiO2. When the amount of SiCO2 used is less than 2 mol,
The maximum working voltage becomes low, and if it exceeds 9 mol, it becomes difficult to make it into a semiconductor.

The amount of Nb2 O5 used as the semiconductor agent is usually 0.1 per 100 moles of TiO2.
0 to 0.16 mol, preferably 0.13 to 0.15 mol, and when the amount of Nb2O5 used is within the above range, the crystal structure of the barium titanate semiconductor ceramic is appropriately refined. However, if the crystal structure is outside the above range, it will not be possible to simultaneously make the crystal structure appropriately finer and to make it sufficiently semiconductive.

The amount of MnCO3 used as the additive is usually 0.03 to 0 per 100 moles of TiO2.
．． 07 mol, preferably 0.04 to 0.06 mol. If the amount of MnCO3 used is less than 0.04 mol, the maximum working voltage will be low, and if it exceeds 0.07 mol, it will be difficult to make a semiconductor. .

The amount of SiO2 used as the additive is usually 2.0 to 3.0 per 100 moles of TiO2.
mol, preferably 2.0 to 2.8 mol, and the SiO
If the amount of 2 used is less than 2.0 moles, it will be difficult to make it into a semiconductor, and if it exceeds 3.0 moles, the sintered bodies will be violently fused together during sintering.

The amount of Al2O3 used as the additive is usually 0.05 to 100 moles of TiO2.
1.0 mol, preferably 0.08 to 0.5 mol, and if the amount of Al2O3 used is less than 0.05 mol, practical specific resistance and high working voltage cannot be obtained. 1
．． If the amount exceeds 0 mol, it becomes difficult to make a semiconductor.

The composition for barium titanate-based semiconductor ceramics and the method for producing barium titanate-based semiconductor ceramics of the present invention will be explained.

[0023] A barium titanate-based semiconductor porcelain composition prepared by blending each component of the main raw material, a semiconducting agent, and an additive in a desired composition ratio and preferably pure water are mixed in a weight ratio of, for example, 1.
: charged into a ball mill at a ratio of 1:1 and wet-pulverized and mixed for usually 10 to 40 hours, preferably 15 to 25 hours, and the resulting slurry is filtered, dehydrated, and dried to dissolve polyvinyl alcohol (PVA) and polyvinylpyrrolidone. (PVP), methylcellulose (MC), pure water, and other binders are mixed and molded at a molding pressure of 0 to 1000 kg/cm2.G, preferably 100 to 500 kg/cm2.G, transferred to a heat-resistant sheath container, and heated in an electric furnace. Usually 1000
Calcinate at a temperature of ~1100°C, preferably 1025~1075°C for usually 30 minutes to 10 hours, preferably 1 to 3 hours, then add pure water at a weight ratio of 1:1 and boil in a ball mill for usually 10 minutes. The mixture is wet-pulverized and mixed for ~40 hours, preferably 15-25 hours, and the resulting mixture is filtered, dehydrated, and dried, and then an organic solvent such as PVA is added and mixed as a binder, and the mixture is granulated, for example, into granules. , molding pressure 500~
2500kg/cm2・G, preferably 1000
Press molded at ~2000kg/cm2・G,
Next, it is charged into a heat-resistant sheath container, and the temperature is usually 1250 to 130
Usually 0.5-1280°C, preferably 1250-1280°C
Sinter for 3 hours, preferably 1-2 hours, then typically 50
~500℃/hr, preferably 100-300℃/hr
The barium titanate semiconductor ceramic of the present invention can be obtained by cooling to room temperature at a cooling rate of .

[0024]

Effects of the Invention According to the present invention, BaC as the main raw material
O3, PbO, CaCO3, SrCO3 and T
iO2, Nb2O5 as a semiconducting agent, MnCO3 as an additive, SiO2 and Al2O3
By selecting each of these and specifying their blending ratio, we have created a product with a fine crystal structure, practical resistivity at room temperature, high maximum operating voltage, and a switching temperature in the high temperature range of 200°C or higher. Provided are barium titanate-based semiconductor porcelain and barium titanate-based semiconductor porcelain compositions used in the production thereof. Therefore, when the barium titanate-based semiconductor porcelain of the present invention is applied to various types of heaters as a constant temperature heating element, it is possible to provide a product with a higher maximum operating voltage than before, that is, a highly reliable product. In addition, when designing a product that has the same performance and reliability as conventional products, it is possible to create a lighter and thinner product because the maximum operating voltage per unit thickness of the semiconductor porcelain is high. Therefore, it is very useful industrially.

[0025]

EXAMPLES The present invention will now be explained in more detail with reference to Examples and Comparative Examples.

Example 1. BaCO3, PbO, CaCO3, SrCO3,
TiO2, Nb2O5, MnCO3, SiO2
, Al2O3 according to the formulations shown in Table 1, and pure water at a weight ratio of 1:1 were charged into a nylon ball mill. , after wet pulverization and mixing for 20 hours,
The resulting slurry was dehydrated, dried, mixed with a PVA binder, and molded at a diameter of 50 m at a molding pressure of 500 kg/cm2/G.
It was molded into a disk shape with a thickness of 10 mm and was calcined in an electric furnace at 1050° C. for 2 hours. The calcined disks were roughly crushed, then pure water was added thereto at a weight ratio of 1:1, and the slurry was wet-pulverized and mixed for 20 hours in a nylon ball mill, and the resulting slurry was dehydrated. , dried, mixed with a PVA binder, and granulated. This granulated powder was molded to a diameter of 16 mm and a thickness of 1 at a molding pressure of 2000 kg/cm2・G.
It was molded into a disk shape of mm in diameter, sintered in an electric furnace at 1250°C for 2 hours, and then cooled to room temperature at a cooling rate of 200°C/hr. Silver electrodes were baked on both sides of the sintered body thus obtained to obtain a measurement sample.

Regarding this sample, the specific resistance value at room temperature (25° C.), the switching temperature, and the maximum operating voltage per unit thickness were measured, and the values are shown in Table 2.

Among the various characteristics described above, the "switching temperature" is the temperature at which the resistance value of the sample reaches a resistance value twice the minimum value. "Maximum operating voltage per unit thickness" is the effective value of the voltage (Vrms) at which the resistance value of the sample reaches its maximum when a 50Hz AC voltage is applied to the sample and the voltage is gradually increased. is the thickness of the sample (mm
) is the value divided by

Further, FIG. 1 shows a photograph of the surface structure of the sintered body obtained in Example 1, observed with a metallurgical microscope.

Examples 2 to 13 and Comparative Examples 1 to 10 Table 1
A barium titanate-based semiconductor porcelain composition was prepared according to the formulation shown in Example 1, and the barium titanate-based semiconductor porcelain obtained in the same manner as in Example 1 was subjected to the same characteristic tests as in Example 1. are shown in Table 2. However, the firing time of Example 2 was 1 hour, and the firing time of Example 10 was 3 hours. Further, FIG. 2 shows a photograph of the surface structure of the sintered body obtained in Comparative Example 9, which was observed using a metallurgical microscope.

[0031]

[Table 1]

[0032]

[Table 2]

[Brief explanation of the drawing]

FIG. 1 is a micrograph showing an example of the surface structure of barium titanate-based semiconductor ceramic of the present invention.

FIG. 2 is a micrograph showing an example of the surface structure of barium titanate-based semiconductor ceramic for comparison.

Claims (2)

[Claims] Claim 1: BaCO3 and PbO as main raw materials
, CaCO3, SrCO3 and TiO2, Nb2O5 as a semiconducting agent, MnCO as an additive
3. A barium titanate-based semiconductor ceramic composition comprising SiO2 and Al2O3, the TiO2
Per 100 mol, BaCO3 50-80 mol, Pb
O20-40 mol, CaCO3 3-8 mol, SrCO
3 2-9 mol, Nb2O5 0.10-0.16 mol, MnCO3 0.03-0.07 mol, SiO2
2.0-3.0 mol and Al2O3 0.05-1
．． The above-mentioned barium titanate-based composition for semiconductor ceramics, which contains 0 mol of each. 2. The barium titanate-based semiconductor ceramic composition according to claim 1 is wet-pulverized and mixed, and after dehydration and drying,
Calcinate with hot air at 1000-1100℃, wet pulverize and mix again, dehydrate and dry, mix with binder and mold.
Barium titanate-based semiconductor porcelain obtained by sintering at a temperature of 250 to 1300°C for 0.5 to 3 hours.