JPH04324901A - Manufacture of barium titanate porcelain semiconductor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is directed to PTC (Positive Temperature Coating) which can be used in many application fields as a planar element such as a low-temperature heater or a temperature sensor.
e Coefficient Thermistor)
The present invention relates to a method for manufacturing a barium titanate-based ceramic semiconductor having characteristics.

0002

[Prior Art] Barium titanate-based ceramic semiconductors, which have the PTC characteristic of having a positive temperature coefficient of resistance at temperatures above the Curie point and having very low resistivity at room temperature, have conventionally been made using titanium containing a Curie point shifting substance. A powder is prepared by adding a semiconducting agent, etc. to a barium acid composition, and after kneading this powder with a binder such as a resin that disappears at low temperatures, this is pressure-molded into a predetermined shape, and then is molded at a high temperature. It is manufactured by a firing method.

0003

[Problems to be Solved by the Invention] However, with the conventional manufacturing method of firing a molded body produced by pressure forming as described above, it is difficult to produce a molded body of a large size, and The more likely it is that damage will occur during firing. In particular, even if it is kneaded with a resin and molded into a green sheet, warping and the like occur during firing, making it impossible to stably manufacture large-area PTC elements.

0004

[Means for Solving the Problems] In order to solve the above-mentioned problems, the method for manufacturing a barium titanate-based ceramic semiconductor of the present invention involves dispersing barium titanate-based semiconductor powder in a binder liquid to produce a paste. , which is characterized in that it is applied to the surface of a zirconia plate and then fired.

[0005]

[Operation] In the above method, a barium titanate ceramic semiconductor is formed into a film covering the surface of a zirconia plate. In this case, a paste in which barium titanate-based semiconductor powder is dispersed is first prepared, and a barium titanate-based ceramic semiconductor is formed as a sintered body that maintains almost the same shape of the paste applied to the surface of the zirconia plate. be done. Therefore, it is possible to produce a barium titanate ceramic semiconductor having a larger area depending on the size of the zirconia plate. In addition, since the zirconia plate functions as a support plate during firing, deformation such as warping during the firing process is suppressed, and a sintered body with the desired shape can be stably produced along the surface shape of the zirconia plate. Ru. The zirconia plate described above hardly reacts with the barium titanate-based semiconductor powder, and therefore, after the above-mentioned firing, it is formed as a homogeneous sintered film with a dense structure. A barium titanate-based ceramic semiconductor having PCT characteristics equivalent to that obtained by the above method has been obtained.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

A barium titanate ceramic semiconductor according to the present invention was manufactured through steps P1 to P6 shown in FIG. That is, first, barium titanate-based semiconductor powder was produced (P1), and then this powder and a binder were mixed to produce a paste in which the powder was uniformly dispersed (P2). Next, this paste is applied onto a zirconia plate, dried (P3), and then fired (P3).
4). As a result, an evaluation sample was prepared in which a barium titanate ceramic semiconductor was formed in the form of a film on a zirconia plate. Electrodes were further formed on the sample thus obtained (P5
), and then the electrical characteristics were measured (P6).

[0008] Hereinafter, specific manufacturing conditions in each of the above steps,
and the measurement results of the characteristics will be explained.

In the process of producing barium titanate semiconductor powder, first, 680.72 g of anhydrous barium carbonate (BaCO3, manufactured by Sakai Chemical Co., Ltd., BW-KL) and 290 g of high-purity titanium dioxide (TiO2, manufactured by Toho Titanium Co., Ltd.) ．．
12g, anhydrous strontium carbonate (SrCO3, manufactured by Honjo Chemical Co., Ltd.) as a Curie point transfer substance 26.80
g, manganese carbonate (MnCO3, manufactured by Wako Pure Chemical Industries, Ltd., 99.9%) as a mineralizing agent, 0.2087 g, silicon dioxide (SiO2, manufactured by Rare Metallic Co., Ltd., 99%) as a stabilizer.
．． 9%) 1.0908g, antimony trioxide (Sb2O3, manufactured by Rare Metallic Co., Ltd., 99.9g as a semiconducting agent)
%) 1.0584g, put it in a 5 liter capacity ball mill, add 3.5 liters of water and a diameter of 25 mm.
40 nylon-coated iron balls and 2
After mixing the powder for 4 hours, it was filtered and the mixture was heated to 130%
Dry at ℃.

[0010] Thereafter, the dry mixture was put into a mold [6].
5mm (diameter) x 45mm (height)], 150kg
It was molded under pressure of /cm2. Next, the molded product was placed in an electric furnace, heated at a temperature increase rate of 180° C./hour, and calcined at 1150° C. for 2 hours. This calcined product was ground in a mortar to obtain barium titanate semiconductor powder.

[0011] In the paste production process, the above powder 500
Put g into a ball mill and add 15wt% as binder liquid.
Add 75 g of a polyvinyl alcohol aqueous solution, and further add 25 g of a dispersant (Paskin M30, manufactured by Kyoei Co., Ltd.), 3 g of a dispersant (Oricox KD800, manufactured by Kyoei Co., Ltd.), 2 g of an antifoaming agent (Solhome CR500, manufactured by Kyoei Co., Ltd.), and 0.0 g of ion-exchanged water.
5 liters and 20 20 mm diameter nylon coated iron balls were added and mixed for 24 hours. In this way, a paste was prepared in which barium titanate semiconductor powder was dispersed in a binder liquid.

In the coating process on the zirconia plate, as shown in FIG.
× 5 mm thick), paste 2 prepared as above was applied to the surface to form a coating film approximately 1 mm thick, and heated to
It was dried at.

[0013] Thereafter, it was placed in an electric furnace and fired at 1360°C for 1 hour.

By the above firing, a film-shaped sintered body 3 covering the surface of the zirconia plate 1 is obtained. In order to evaluate the electrical properties of this sintered body 3, as shown in FIG.
An electrode 4 was formed on the surface of the sample, and an evaluation sample 6 of a barium titanate ceramic semiconductor was prepared. After applying ohmic silver paste (manufactured by Degussa), the electrode 4 was
Baking was performed at 0°C for 5 minutes, and the surface was further coated with
The cover was formed by applying a silver electrode and baking at 560° C. for 5 minutes.

[0015] The sample 6 was attached to a sample holder for measurement, and a measurement tank (manufactured by Yamato Co., Ltd., FINEOVEN D
H42), and changes in electrical resistance with respect to temperature changes from room temperature to 200° C. were measured using a DC resistance meter (manufactured by YHP, Multimeter 3478A).

An example of the results is shown in FIG. As shown in the figure, sample 6, which was manufactured by applying a paste on a zirconia plate and firing it, has excellent PTC characteristics, such as having low electrical resistance at room temperature and rapidly increasing electrical resistance as the temperature rises.

[0017] Furthermore, using a scanning electron microscope, the sintered body 3
When the surface of the sample was observed, it was confirmed that this was a sintered body composed of dense barium titanate particles. In other words, since the zirconia plate 1 hardly reacts with the barium titanate semiconductor material, sintering of the barium titanate semiconductor material progresses without impurities entering from the zirconia plate 1 side during the firing process. do. This results in a sintered body 3 having good PCT characteristics.
is formed. Further, there is no unnecessary reaction layer at the interface, and as a result, the sintered body 3 is firmly adhered to the zirconia plate 1, and the sintered body 3 itself is a film having high strength. It is formed as.

The barium titanate-based ceramic semiconductor manufactured by the manufacturing method of this example can be used as an industrial material such as temperature sensors and low-temperature heating planar heaters, and as a high-performance material for thermal fuses and switching power supplies. Comparators, protection circuits for electrolytic capacitors, color TV automatic degaussing devices, motor starting devices for automobiles, heating prevention devices for electronic equipment, delay elements, timers, liquid level gauges, non-contact switches, relay contact protection devices, and many other fields. It can be used in

[0019]

Effects of the Invention As described above, the method for manufacturing a barium titanate-based ceramic semiconductor of the present invention involves dispersing barium titanate-based semiconductor powder in a binder liquid to make a paste, and applying this to the surface of a zirconia plate. After coating, it is fired.

[0020] As a result, a sintered body is formed in a shape that substantially maintains the shape of the coating film on the surface of the zirconia plate, so a barium titanate-based ceramic semiconductor having a larger area can be produced in accordance with the area of the zirconia plate. I can do that. Further, during firing, the zirconia plate functions as a support plate, and deformation such as warping during the firing process is suppressed. As a result, it is possible to easily manufacture a device with a larger area with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the manufacturing process of a barium titanate-based ceramic semiconductor manufactured by applying the present invention.

FIG. 2 is a perspective view showing a zirconia plate coated with paste during the above manufacturing process.

FIG. 3 is a perspective view of an evaluation sample produced through the above manufacturing process.

FIG. 4 is a graph showing an example of the measurement results of temperature and electrical resistance of the evaluation sample.

[Explanation of symbols]

1 Zirconia plate 2 Coating film 3 Sintered body

Claims (1)

[Claims] 1. Manufacture of a barium titanate-based ceramic semiconductor characterized by dispersing barium titanate-based semiconductor powder in a binder liquid to make a paste, applying this to the surface of a zirconia plate, and then firing it. Method.