JPS6313316A - Compound for semiconductor porcelain capacitor - 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] [Industrial Application Field] The present invention relates to a composition for semiconductor ceramic capacitors, in particular, compositions containing strontium titanate as a main component and specific additives added thereto, which have dielectric constant, insulation resistance, etc. The present invention relates to a grain boundary insulated semiconductor ceramic capacitor composition with excellent properties.

[Problems to be Solved by the Invention Strontium cotitanate (Sr Ti 03 )-based semiconductor ceramic capacitors have an apparent large dielectric constant and relatively small dielectric loss;
It is widely used as a semiconductor ceramic capacitor because it has better temperature characteristics than the i 03 ) type semiconductor ceramic capacitor. From this point of view, various studies have been conducted on semiconductor ceramic compositions in which calcium titanate is dissolved in strontium titanate.
Inventions described in JP-A-4665, JP-A-57-39520, JP-A-58-21312, etc. have been proposed. These are solid solutions of strontium titanate and calcium titanate, niobium pentoxide as a semiconducting agent,
Those using lanthanum oxide, etc., as well as manganese dioxide,
Although cupric oxide and the like are added, the main purpose of all of them is to improve the temperature characteristics of the dielectric constant and the withstand voltage, and when looking at the dielectric constant, they are not fully satisfactory.

Incidentally, in recent years, as devices have become smaller, capacitors with even larger capacities are desired. In order to increase the capacity of a grain boundary insulated capacitor, it is necessary to increase the size of the crystal grains, and it is generally desirable to grow them to a size of 50 μm or more.

However, as the crystal grains become larger, the proportion of the grain boundary layer per unit area decreases, and the formation of an insulating layer is insufficient, resulting in problems such as a low insulation resistance, although the apparent dielectric constant increases. Requires some ingenuity in insulation treatment.

In view of these conventional problems, the present invention provides a composition for semiconductor ceramic capacitors that can further improve the dielectric constant and produce grain-boundary insulated capacitors that have excellent capacitor properties such as insulation resistance and dielectric loss. The purpose is to

[Means for Solving the Problems] In accordance with the above objectives, the present inventors have conducted various studies on systems in which calcium titanate is dissolved in strontium titanate in order to improve strontium titanate-based semiconductor ceramic capacitors. , a semiconductor made by using niobium pentoxide as a semiconductor agent and adding specific amounts of manganese dioxide, cupric oxide and/or bismuth trioxide! After sintering this porcelain composition, we applied an insulating agent to the porcelain surface and thermally diffused the grain boundary layer, thereby improving the dielectric constant and insulation resistance. It was discovered that an excellent semiconductor porcelain capacitor that is large and has low dielectric loss can be developed, leading to the present invention.

That is, the present invention provides strontium titanate (SrT
i 03 ) 99.9-87.5 mol, calcium titanate (Ca'r+ 03 ) O,t ~12,
Niobium pentoxide (
Nb205) 0.02-1.00-E, manganese dioxide (Mn02) 0.10-1.00-E, cupric oxide (Cub) 0.01-0.85 mol and/or trioxide Bismuth (B1203) 0.01-0.5
There is a composition for a semiconductor ceramic capacitor in which 0 mol is added.

In the present invention, as described above, 99.9 to 87.5 moles of strontium titanate and 0.9 to 87.5 moles of strontium titanate are used.
The main component of the semiconductor ceramic composition is 0.02 to 1.00 mole of niobium pentoxide as a semiconducting agent to a total of 100 moles of 1 to 12.5 moles, and 0.10 mole of manganese dioxide. ~1.00 mol and cupric oxide 0.01
~0.85 mol and/or 0.01 bismuth trioxide
It is characterized by adding ~0.50 mol.

In this composition, if the solid solution amount of calcium titanate relative to strontium titanate is less than 0.1 mol, there is no effect of addition, and if it exceeds 12.5 mol, the dielectric constant decreases and dielectric loss increases. Further, if the amount of manganese dioxide added is less than 0.10 mol, there is no effect of addition, and if it exceeds 1.00 mol, the dielectric constant decreases and dielectric loss increases. If the amount of cupric oxide added is less than 0.01 mol, the insulation resistance will be low, and if it exceeds 0.85 mol, the dielectric constant will decrease and dielectric loss will increase. If the amount of bismuth trioxide added is less than 0.01 mol, there will be no effect, and if it exceeds 0.5 mol, grain growth will be inhibited and the dielectric constant will decrease.

The composition of the present invention having such a composition is sintered and then insulated by applying an insulating agent to its surface.

As the insulating agent used here, a combination of lithium carbonate and bismuth trioxide is preferable because it has a remarkable insulating effect. The mixing ratio of lithium carbonate and bismuth trioxide is preferably in the range of 80 to 25 mol% of lithium carbonate and 20 to 75 mol% of bismuth trioxide. moreover,
In addition to the above insulating agents, alkali carbonates and metal oxides,
For example, a combination of manganese dioxide, cupric oxide, etc. can also be used as an effective insulating agent.

The above-mentioned insulating agent made of lithium carbonate and metal oxide such as bismuth trioxide is dispersed in water and a water-soluble glue or varnish, and applied to both sides of the semiconductor porcelain 1c#f at approximately 5Rg.
A diffusion process is performed at about 1200° C. for 30 minutes, for example.

[Examples] Next, the present invention will be specifically described based on Examples and Comparative Examples.

Examples 1 to 11 and Comparative Examples 1 to 8 Strontium carbonate, calcium carbonate, and titanium dioxide were each weighed so that the proportions of strontium titanate and calcium titanate were as shown in Table 1. In addition, niobium pentoxide, manganese dioxide, cupric oxide, and bismuth trioxide should be mixed in the proportions shown in Table 1 for a total of 100 moles of strontium titanate and calcium titanate. Cupric oxide and bismuth trioxide were each weighed. These were subjected to isothermal pulverization treatment for 24 hours in a wet ball mill, and then dried.

This product was calcined in the air at 1050 to 1150°C for 3 hours, cooled, and then finely pulverized. A binder was added to this powder and it was molded into a disc with a diameter of 15 m under a pressure of 1 ton/cIi.

The molded product was calcined in the atmosphere at 700° C. for 1 hour to remove the binder, and then sintered in a nitrogen or argon stream containing 1 to 10% hydrogen by volume. Sintering was performed at 1400 to 1460°C for 4 hours.

The semi-uniform crystal grain size of the sintered body was 50μ as measured by SEM.
It ranged from m to 100 μm. This sintered body has a first
After applying the insulating agent shown in the table on both sides,
A diffusion treatment was performed at 00° C. for 30 minutes to insulate the grain boundary layer.

Silver electrodes are applied and baked on both sides of this insulated semiconductor porcelain.
It was used for measurement. y, electric constant (ε) and dielectric loss (tanδ
) was measured at frequency lKH2 and 25°C.

Moreover, the insulation resistance was determined by applying a DC voltage of 50 V at 25° C. and using the resistance value after 60 seconds of contact.

These results are shown in Table 1.

Further, the temperature characteristics of the dielectric constant were calculated in the temperature range from -25°C to +85°C with 20°C as a reference, and the results are shown in FIG. In Figure 1, the vertical axis is the dielectric constant (%).
, the horizontal axis indicates temperature ("C).

As shown in Table 1, Examples 1 to 1 are a basic composition of strontium titanate, calcium titanate, and niobium pentoxide, and a specific range of manganese dioxide, cupric oxide, and/or bismuth trioxide. Sample No. 11 has a larger dielectric constant than Comparative Examples 1 to 8, which are outside the scope of the present invention, and also has insulation resistance and dielectric loss within the desired range.

[Effects of the Invention] As explained above, this invention is made by adding specific amounts of manganese dioxide, second steel oxide, and/or bismuth trioxide to a solid solution of strontium titanate and calcium titanate using niobium pentoxide as a semiconducting agent. The ceramic composition of the invention can provide a capacitor material with a high dielectric constant and excellent dielectric loss and insulation resistance.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the temperature characteristics of dielectric constant.

Claims (1)

[Claims] 1. Strontium titanate 99.9 to 87.5 mol,
For a total of 100 moles consisting of 0.1 to 12.5 moles of calcium titanate, 0.02 to 1.00 moles of niobium pentoxide, 0.10 to 1.00 moles of manganese dioxide, and 0.01 to cupric oxide. A composition for a semiconductor ceramic capacitor containing 0.85 mol and/or 0.01 to 0.50 mol of bismuth trioxide.