JPS6050006B2 - High dielectric constant porcelain composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high dielectric constant ceramic composition with excellent temperature characteristics suitable for use in ceramic capacitors, electrostrictive elements, and the like.

Conventionally, BaTiO has been used for the above applications.

, BaSnO3, CaTiO. Porcelain made by modifying this with various additives has been put into practical use. For these porcelains, increasing the dielectric constant around room temperature increases the temperature change rate of the dielectric constant, while decreasing the temperature change rate of the dielectric constant decreases the dielectric constant at normal temperature. It has been difficult to obtain porcelain with a small rate of temperature change. The present invention improves these drawbacks and provides a ceramic composition that has a large dielectric constant and a small rate of change in dielectric constant with temperature. That is, the composition of the present invention contains XPbNi, I3Nb2hO3-(1-X)Pb2'
n, l3Nb2laO3 (however, 0.2≦X≦0.8
) (15% or less of Pb atoms are Br, Ca
and a composition containing one or more of Ba atoms substituted with one or more of the following. The characteristics that a dielectric material should have vary depending on its use, but materials such as ceramic capacitors and electrostrictive elements require a material with a large dielectric constant and a small rate of temperature change.

Note that a high dielectric constant is important for downsizing capacitors and the like. Furthermore, in order to obtain stable characteristics over a wide temperature range, it is necessary to reduce the temperature change rate of material constants, especially the dielectric constant. The present invention provides a porcelain composition suitable for such uses. The present invention will be explained below using examples. Example 1 PbO9Ni9Nb2O59ZnO as raw material
9BaCO3, SrCO.

, CaCO. These were weighed and mixed in the composition ratios shown in Table 1 using a 100% polyester, calcined at 850° C. for 2 hours, and then wet-pulverized using a ball mill. After drying the pulverized material, it was pressure-molded into a cylindrical shape with a diameter of 137 wt and a length of about 10 wl using an aqueous solution of polyvinyl alcohol as a binder, and this was placed in a magnesia porcelain container.
It was fired at 1600C for 2 hours. Thickness of fired porcelain is 1=
After cutting Cr--Au as electrodes on both sides, the dielectric constant (E) and dielectric loss tangent (D) were measured at 1 kHz at room temperature. The temperature change rate of dielectric constant was measured in the range of -25°C to 85°C with 20°C as a reference. The results are shown in Table 1. No. 1 in Table 1. No. 1 and No. 17 are examples outside the scope of the present invention. 2 to 16 are examples of the present invention.

As is clear from Table 1, the porcelain made of the composition within the scope of the present invention has a large dielectric constant (εr) (4080-81
80) and a relatively small temperature change rate of dielectric constant (-25 to 8
-51% to 78%) in the temperature range of 5°C. That is,
This is XPbNlll3Nb2l3O3-(1-X)
PbZnl/3NY) 2no. Within the limited range of the 03 series (
X=0.2 to 0.8), it exhibits a large dielectric constant of 4000 or more.

Further, the firing temperature is within the range of 980 to 1140°C,
Another feature of the present invention is that it is significantly lower than conventional BaTlO3-based materials. As described above, the composition of the present invention has a large dielectric constant, a small temperature change rate, and a low firing temperature. It is of high value.

Example 2 Voltage (4) between both electrodes of a disk-shaped sample manufactured by the method described in Example 1. 01 Hz) was applied, and the electrostriction in the thickness direction of the sample at that time was measured using a differential transformer.

Strain was measured by immersing the sample in silicone oil. NO
．． For samples 3 and 5, the applied voltage was 20KV/C7! In the case of , the electrostriction is 0.48X10-3 and 0.39 respectively at room temperature
It was ×10-3. Further, the change in this strain due to temperature was 11% and 23%, respectively, in the temperature range of -20 to 60°C. Since the composition of the present invention has a large electrostriction and a small change in strain due to temperature, it is suitable for various variable elements such as a head drive element for VTR auto-tracking, a mirror control element, and a bonded type flexible element. As described above, the high dielectric constant ceramic composition of the present invention has a large dielectric constant, a small change in dielectric constant due to temperature, and a significantly low firing temperature, so it is useful as a material for ceramic capacitors and has a large electrostriction. Moreover, since it has the feature of small change due to temperature, it has high utility value as a material for various displacement elements.

In addition, in the present invention, compositions in which the value of x is less than 0.2, the value of , excluded from the scope of the present invention because the dielectric constant becomes small.
The scope of the present invention is limited to compositions having a dielectric constant of 4000 or more.

Claims (1)

[Claims] 1 XPbNi_1/_3Nb_2/_3O_3-(1
-X) PbZn_1/_3Nb_2/_3O_3 (however, 0.2≦X≦0.8),
Or a high dielectric constant ceramic composition characterized by having this composition as a main component. 2. The high dielectric constant ceramic composition according to claim 1, wherein 15% or less of the Pb atoms are replaced with one or more of Sr, Ca, and Ba atoms.