JPS5920906A - Dielectric porcelain composition - 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 The present invention has a high dielectric constant, has a small change in dielectric constant over a wide temperature range, has a very small dielectric loss tangent value, and has a fine particle size, making it easy to make into porcelain. This invention relates to a certain dielectric ceramic composition.

Conventionally, as a composition with a high dielectric constant and a small temperature change rate, a composition in which a bismuth compound such as bismuth stannate, bismuth titanate, or bismuth zirconate is added to barium titanate to flatten the temperature characteristics has been used. However, recent ceramic capacitors are required to be small and large in capacity.
Many multilayer ceramic capacitors are used. When a dielectric composition containing a bismuth compound is used for this purpose, there is a drawback that the internal electrodes made of platinum or geladium are severely corroded.

Unfortunately, if the composition contained a bismuth compound with a high vapor pressure, the bismuth would evaporate during firing, making it extremely difficult to obtain a ceramic with close edges. Furthermore, the dielectric constant was as low as 2000 or less, which did not satisfy the demand for smaller size and larger capacity.

The present inventors have conducted intensive research to provide a high dielectric constant porcelain composition that solves the above-mentioned drawbacks, and have found that by adding niobium pentoxide, calcium oxide, and zinc oxide to barium titanate, it can be used over a wide temperature range. The present inventors have discovered that a high dielectric constant composition having a small change in dielectric constant over a range and a very small value of dielectric loss tangent can be obtained, and has completed the present invention.

The basic gist of the present invention is that barium titanate 86.0-98.9 mol%, niobium pentoxide 0,
5-3.0 mo1%, calcium oxide 0, 5-9.0
mo1%, zinc oxide from 0.1 to 2.0 mol, and niobium pentoxide and calcium oxide within this range.
A dielectric ceramic composition characterized by having an ol ratio of 1:1 to 1:4. Barium titanate is the main ingredient,
Niobium pentoxide has the effect of reducing the rate of change in dielectric constant with temperature, and the rate of change can be further reduced by adding zinc oxide. Calcium oxide has the effect of lowering the firing temperature and preventing abnormal grain growth. Here, the molar ratio of niobium pentoxide to calcium oxide is preferably in the range of 1:1 to 1:4, and the most preferred combination is 2 m01 of calcium oxide to 1 mol of niobium pentoxide.

By changing the composition ratio within the above range, the dielectric constant is 2000 to 3500, and the temperature change rate is 5℃ to -1.
Within ±20 inches over 25℃, dielectric loss tangent 0.9%
A dielectric ceramic with high insulation resistance can be obtained as follows. In particular, since the value of the dielectric loss tangent is small, it is possible to provide a dielectric ceramic that can withstand usage conditions with high electric field strength.

Next, the reasons for limiting each component of the present invention will be explained based on test results. When barium titanate is less than 86.0 mo1%, the dielectric constant is small and its rate of temperature change becomes large.
If it exceeds mol %', sintering becomes difficult. If the content of niobium pentoxide is less than 0.5 mo1%, the dielectric loss tangent will be too high and sintering will be difficult.If it exceeds 3.0 mo1%, the dielectric constant will be small and its temperature change rate will be large. Zinc oxide is 0.1
If the mo amount is less than 1%, there is no effect of reducing the temperature change rate of the dielectric constant, and if it exceeds 2.0 mo1%, the value of the dielectric loss tangent increases and the insulation resistance further deteriorates. If calcium oxide is less than 0.5 mol %, it will not be effective in lowering the firing temperature and preventing abnormal grain growth, and if it exceeds 9.0 mol %, the temperature change rate of the dielectric constant will become steeper, and the value of the dielectric loss tangent will also increase. Become.

The molar ratio of niobium pentoxide and calcium oxide is most preferably 1:2; when calcium oxide is less than 1:1, the effect of preventing abnormal grain growth is small, and when calcium oxide is more than 1:4, the dielectric constant changes with temperature. rate increases.

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

First, mix barium carbonate and titanium oxide in a 1:1 ratio,
It was calcined at 100°C to obtain fine barium titanate powder.

It was determined by powder X-ray diffraction that the calcined powder obtained here was completely converted into barium titanate. After firing, niobium pentoxide, zinc oxide, and calcium oxide were weighed out to the norium titanate in the mixing ratio shown in the table below, and a ball mill made of hard resin was used to prevent contamination of impurities.
After time mixing, dehydration and drying, molding pressure 3 tons
/ ca to have a diameter of 16mm and a thickness of 0.6m, and the molded product was fired for 1 hour at the firing temperature shown in the table below.
~15 was obtained.

Silver electrodes were baked on both sides of these samples, and the dielectric constant, dielectric loss tangent, and temperature change rate of the dielectric constant were measured using a YAP digital LCR meter model 4274A at a measurement temperature of 25°C and a measurement voltage of 1. It was determined by measurement using OV rms 1 and a measurement frequency of 1.0 KHz. Insulation resistance is YHP model 432
Using 9A, the applied voltage was 100v% and the value was determined for 1 minute. The temperature change rate of the dielectric constant was measured in the range of -55°C to +125°C, and the dielectric constant at 25°C was used as a reference. The test conditions and results are shown in the table below.

In the above table, sample numbers 1 to 10 are examples within the scope of the present invention, and samples 11 to 15 are comparative examples outside the scope. The drawing shows the rate of change in dielectric constant of Sample No. 5 with temperature. In all of the examples of sample numbers 1 to 10 within the scope of the present invention, the rate of change in dielectric constant with temperature is small, and the dielectric constant is 2000.
An extremely excellent dielectric ceramic having a large dielectric loss tangent value and a small dielectric loss tangent value has been obtained.

As described above, the dielectric ceramic composition within the scope of the present invention has practical dielectric constant, dielectric loss tangent, and dielectric constant temperature characteristics,
In particular, it has a small dielectric loss tangent value and does not contain a bismuth compound, making it ideal as a dielectric material for use in multilayer ceramic capacitors with high electric field strength.

[Brief explanation of the drawing]

The drawing is a graph showing the rate of change of dielectric constant with temperature of one sample of the composition according to the present invention. Procedural amendment September 27, 1980 Kazuo Wakasugi, Commissioner of the Patent Office 1. Indication of the case 1982 Patent Application No. 129001 2
, Name of the invention Dielectric ceramic composition 3. Name of the person making the amendment Mitsubishi Mining Cement Co., Ltd. (name) 4. Agent 5. Subject of the amendment ``Detailed description of the invention'' in the specification
Column (1) Correct "geradium" in the off-line of page 2 of the specification λ to "palladium." (2) In the 11th line of the same page, ``precise'' is corrected to ``precise''. (3) Correct ri:IJ on page 5, line 16 of the same as "rml ratio 1:1". (4) Same as above, page 6, line 8, “YAP J is corrected to r YHP J.

Claims (1)

[Claims] Barium titanate 86.0-98.9 mo1%, niobium pentoxide 0.5-3.0 mo1%, calcium oxide 0.
5-9.0 mol %, zinc oxide 0.1-2.0 mo
A dielectric ceramic composition comprising a component range of 1% and characterized in that the molar ratio of niobium pentoxide to calcium oxide is within the range of 1=1 to 1:4.