JPS6020849B2 - dielectric porcelain composition - Google Patents

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 constant value, and has a fine particle size, making it easy to make into porcelain. The present invention relates to a dielectric ceramic composition.

Conventionally, as a composition having 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 is used.

However, recent ceramic capacitors are required to be small and large in capacity, and many multilayer ceramic capacitors are used.For this purpose, when using dielectric compositions containing bismuth compounds, platinum or palladium However, if the composition contains a bismuth compound with a high vapor pressure, the bismuth will evaporate during firing, making it extremely difficult to obtain a delicate ceramic. Furthermore, the dielectric constant was low at 2000 or less, which did not satisfy the demand for smaller size and larger capacity. As a result of extensive research, we have found that by adding niobium pentoxide, calcium oxide, zinc oxide, and manganese dioxide to barium titanate, the change in dielectric constant is small over a wide temperature range, and the value of dielectric constant is extremely small. They found that it could be made into a composition with electrical conductivity, and completed the present invention. o The basic gist of the present invention is that barium titanate 85.70
~98.89 hol%, niobium pentoxide 0.50-0.3
hol%, calcium oxide 0.50-9.0 hol%
%, zinc oxide 0.10-2.0 skin ol%, manganese dioxide 0.01-0.

The dielectric ceramic composition is characterized in that the molar ratio of niobium pentaoxide and calcium oxide is 1:1 to 1:4 within the range of this component.

Barium titanate is the main component, and niobium pentoxide has the effect of reducing the rate of change in dielectric constant with temperature, and by adding zinc oxide, the rate of change can be further reduced. Calcium oxide has the effect of lowering the firing temperature and preventing abnormal grain growth. Conventionally, manganese dioxide was added to prevent reduction during firing of barium titanate-based porcelain, but in the present invention, the value of dielectric support is further reduced, and temperature changes in dielectric constant are prevented. This has the effect of reducing the ratio. Here, the molar ratio of niobium pentoxide and calcium oxide is 1:1 to 1:4.
It is preferably in the range of 1 mol of niobium pentoxide to 1 mol of calcium oxide. By changing the composition ratio within the above range,
The yield rate is 2000-350Q, the temperature change rate is within ±20% from -55℃ to 1125q0, and the dielectric Seifuji is 0.9
% or less, dielectric ceramics with high insulation resistance can be obtained.

In particular, since the yield tangent value is 4.0, it is possible to provide dielectric porcelain that can withstand usage conditions with high noise field intensity. Next, the reasons for limiting each component of the present invention will be explained based on test results.

If barium titanate is less than 8570 hol%, the dielectric constant is small and its temperature change G rate becomes large, making it difficult to use. 89ho
If it exceeds 1%, sintering becomes difficult. Niobium pentoxide is 0.5
When the hol% is full, the dielectric constant is large and the dawn stripes are even more difficult, and when the hol% is over 3.00 hol%, the dielectric constant is small.
The rate of temperature change increases. Zinc oxide is 0.1 ho
If it is less than 1%, there is no effect of reducing the rate of change in dielectric constant with temperature, and if it exceeds 2.0%, the value of the dielectric constant increases and the insulation resistance further deteriorates. Calcium oxide is 0
．． If the hol% is less than 9.0 hol%, it is not effective in reducing the firing temperature and preventing abnormal grain growth, and if it exceeds 9.0 hol%, the temperature change rate of the dielectric constant becomes large and the value of the dielectric constant becomes large. If the amount of manganese dioxide is less than 0.01 mol%, there is no effect of reducing the dielectric positive temperature, and if it exceeds 0.35 mol%, the insulation resistance will deteriorate. m of niobium pentoxide and calcium oxide
The oi ratio is most preferably 1:2; if the calcium oxide content is less than 1:1, the effect of preventing abnormal grain growth will be small, and if the calcium oxide content is more than 1:4, the temperature change rate of the dielectric constant will increase.

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 of the present invention is exceeded.

First, barium carbonate and titanium oxide were mixed at a molar ratio of 1:1 and calcined at 110 pi to obtain fine powder of barium titanate.

It was determined by powder X-ray diffraction that the pseudomorphic powder obtained here was completely converted into barium titanate. This barium titanate was calcined with niobium pentoxide, zinc oxide, calcium oxide, and manganese dioxide, and then weighed out so as to have the compounding ratio shown in the table below.In order to prevent the contamination of impurities, a ball mill made of hard resin was used to prepare two feeds. After wet mixing for an hour, dehydrating and drying, the molding pressure was 3 tons to form a willow with a diameter of 16 mm and a thickness of 0.6. 15 was obtained. Silver electrodes were baked on both sides of these samples, and the dielectric constant was ``dielectric positive'', and the temperature change rate of the dielectric constant was YH.
Using a P digital LCR meter model 427, the measurement temperature is 25q0, the measurement voltage is 1.0V, and the measurement frequency is 1.
．． It was determined by measurement using a plate Hz.

Insulation resistance was determined by using YHP model 432 carp and applying voltage l.
ooV was determined from the 1 minute value. Temperature change rate of dielectric constant is -5
It was measured in the range of 5° C. to 1125 pm, and the dielectric constant at 25 qC was used as the standard. 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 20.
It has a large value of 0.00 or more, and has a value of 4.00, making it possible to obtain extremely high quality porcelain. As mentioned above,
The dielectric ceramic composition within the scope of the present invention has a practical dielectric constant,
It has dielectric constant and temperature characteristics of 0 degrees, has a particularly small value of dielectric constant, and does not contain bismuth compounds, making it ideal as a dielectric material for use in multilayer ceramic capacitors with high electric field strength.

[Brief explanation of the drawing]

5 The drawing is a graph showing the temperature change rate of the dielectric constant of one sample of the composition according to the present invention.

Claims (1)

[Claims] 1 Barium titanate 85.70-98.89 mol%
, niobium pentoxide 0.50-3.00 mol%, calcium oxide 0.50-9.00 mol%, zinc oxide 0.10
~2.00mol%, manganese dioxide 0.01~0.3
A dielectric ceramic composition comprising a component range of 0 mol % and characterized in that the molar ratio of niobium pentoxide to calcium oxide is within the range of 1:1 to 1:4.