JPS6131926B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high dielectric constant ceramic having excellent temperature characteristics suitable for use in ceramic capacitors, electrostrictive elements, and the like. Conventionally, BaTiO ₃ , BaSnO ₃ ,
Porcelain containing CaTiO ₃ as its main component and modified 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 room temperature. It has been difficult to obtain porcelain with a small rate of temperature change. The present invention aims to improve these drawbacks and provide a ceramic material that has a large dielectric constant and a small rate of change in dielectric constant with temperature. That is, the present invention provides XPbNi _1/3 Nb _2/3 O ₃ −YPbTiO ₃ −
Among the ceramic compositions mainly composed of ZBaZn _1/3 Nb _2/3 O ₃ , PbNi _1/3 Nb _2/3 O ₃ , PbTiO ₃ ,
High dielectric constant composed of compositions in a rectangle with compositions A, B, C, and D as vertices in triangular coordinates with BaZn _1/3 Nb _2/3 O ₃ as the vertices, or with this composition as the main component Porcelain (however, at X+Y+Z=100,
A is X=88, Y=11, Z=1, B is X=0, Y=
55, Z=45, C has X=0, Y=70, Z=30, and D has X=58, Y=41, Z=1 [mol%]. The present invention also includes compositions in which 20 mol% or less of Pb is replaced with one or more of Sr, Ca, and Ba. 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. In addition, in order to obtain stable characteristics over a wide temperature range, it is necessary to reduce the rate of change in dielectric constant with temperature when the material is constant. The present invention provides high dielectric constant porcelain suitable for such uses. The present invention will be explained below with reference to Examples. Example 1 Raw materials PbO, NiO, Nb ₂ O ₅ , TiO ₂ , ZnO,
Using BaCO ₃ , SrCO ₃ , and CaCO ₃ , these
Weighed and mixed the composition ratio shown in the table and heated it to 850℃.
After calcining for 2 hours, the mixture was wet-pulverized in a ball mill. After drying the pulverized product, it was pressure-molded into a cylindrical shape with a diameter of 13 mm and a length of about 10 mm using an aqueous solution of polyvinyl alcohol as a binder, which was placed in a magnesia porcelain container and fired at 1150 to 1300°C for 2 hours. The fired porcelain was cut into 1 mm thick pieces, Cr-Au was deposited on both sides as electrodes, and the dielectric constant (ε
r) and dielectric loss tangent D were measured at 1 KHz and room temperature. Temperature change rate of dielectric constant is -25 with reference to 20℃
Measured in the range of ~85°C. The results are shown in Table 1.

【table】

[Table] In Table 1, Nos. 1, 12, 21, and 26 are examples outside the scope of the present invention, and Nos. 2 to 11, 13 to 20, and 22 to 25 are examples within the scope of the present invention. It is. As is clear from Table 1, the porcelain made of the composition within the scope of the present invention has a large dielectric constant (3040~
13950) and a relatively small temperature change rate of dielectric constant (−
-55% to 65% in the temperature range of 25 to 85°C). In the present invention, the BaZn _1/3 Nb _2/3 O ₃ component is
PbNi _1/3 Nb _2/3 O ₃ −PbTiO ₃ −BaZn _1/3 Nb _2/3 O ₃
In the system, it acts to alleviate the sudden change in dielectric constant due to temperature near the Curie point, and as a result, a composition whose dielectric constant changes little due to temperature can be obtained. In addition, in the present invention, Pb can be replaced with Sr,
By substituting one or more of Ca and Ba, the change in dielectric constant due to temperature can be reduced, and the temperature gradient thereof can be changed. As described above, the composition of the present invention has a large dielectric constant and a small rate of change with temperature, and is therefore useful as a ceramic capacitor material. Example 2 A voltage (measured at 0.01 Hz) was applied between both electrodes of the disk-shaped sample prepared by the method described in Example 1, and the electrostriction in the thickness direction of the sample at that time was measured using a differential transformer. It was measured using Note that the sample was immersed in silicone oil for measurement. For samples No. 4, 6, and 23 in Table 1, when the applied voltage is 20 KV/cm, the changes in thickness (strain) are 1.0×10 ^-3 , 0.85×10 ^-3 , and 0.88×, respectively.
It was 10 ^-3 . Additionally, the temperature-dependent change in this strain is up to 29% and 29%, respectively, in the temperature range of -20 to 60℃.
The percentages were 18% and 34%. As described above, the composition of the present invention has a large electrostriction and can produce a porcelain whose strain changes little with temperature. Suitable for various displacement elements such as In other words, the high dielectric constant ceramic of the present invention not only has a large dielectric constant and a small change due to temperature, but also has a large strain due to electrostriction and a small change due to temperature. It has industrial value in applications such as In addition, in the present invention, if X is less than mol%, the effect of reducing the change in dielectric constant due to temperature is small, and the compositions outside the rectangular area with compositions A, B, C, and D as vertices in the figure are dielectric. On the other hand, compositions in which the substitution of Pb with Sr, Ba, and Ca exceeds 20 mol % have a small dielectric constant, and are therefore excluded from the scope of the present invention. limited to. Note that vertex A is X=88, Y=
11, Z = 1, and vertex B is X = 0, Y = 55, Z
=45, vertex C is X=0, Y=70, Z=30, vertex D
is X=58, Y=41, Z=1 (all units are mol%).

[Brief explanation of the drawing]

The figure is a composition diagram of the high dielectric constant ceramic according to the present invention.

Claims (1)

[Claims] 1 XPbNi _1/3 Nb _2/3 O ₃ −YPbTiO ₃ −
Among the porcelain compositions containing ZBaZn _1/3 Nb _2/3 O ₃ as the main component (X+Y+Z=100),
PbNi _1/3 Nb _2/3 O ₃ , PbTiO ₃ , BaZn _1/3 Nb _2/3 O ₃
A high dielectric constant porcelain comprising a composition within a rectangular region having compositions A, B, C, and D as vertices in triangular coordinates having vertices at , or having the composition as a main component. However, A is X=88, Y=11, Z=1, B is X
=0, Y=55, Z=45, C is X=0, Y=70, Z
=30, D is X=58, Y=41, Z=1 (mol%). 2. The high dielectric constant ceramic according to claim 1, wherein 20% or less of the Pb atoms are replaced with one or more of Sr, Ca, and Ba atoms.