JPH0247424B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a porcelain composition, particularly a porcelain composition with a high dielectric constant, low sintering temperature, and high mechanical strength. It is well known that dielectrics containing barium titanate (BaTiO ₃ ) as a main component have been widely put into practical use as conventional high-permittivity dielectrics. However, for materials whose main component is BaTiO ₃ , the sintering temperature is usually
The high temperature is 1300°C to 1400°C, and especially in the case of multilayer capacitors, the disadvantage is that an expensive noble metal such as platinum or palladium must be used as the main component for internal electrodes suitable for this sintering temperature. Was. Therefore, in order to make it possible to use inexpensive internal electrodes mainly composed of silver, nickel, etc., there has been a strong demand for a dielectric material that can be sintered at as low a sintering temperature as possible, particularly at a temperature of 960° C. or lower. The object of the present invention is to be able to sinter at a temperature of 960°C or less,
The object of the present invention is to provide a ceramic composition having a high dielectric constant, low dielectric loss, and high specific resistance. A further object of the present invention is to provide a composition for a multilayer capacitor that suppresses grain size growth of sintered porcelain, increases sintered density, increases mechanical strength, and has high reliability. In other words, when a chip capacitor is mounted on a board, mechanical strain is applied to the chip capacitor due to the difference in thermal expansion coefficient between the board and the ceramic, which can cause minute cracks or, in severe cases, damage to the chip capacitor. occurs. Furthermore, in the case of dip capacitors coated with epoxy resin or the like, cracks may occur in the porcelain due to the stress of the coated resin. In either case, the lower the bending strength of the porcelain, the more likely it will be cracked and damaged, and the reliability will be lower. Therefore, it is extremely important in practice to increase the mechanical strength of ceramics as much as possible. By the way, Pb(Fe _2/3 W _1/3 ) O ₃ −PbZrO ₃ is one of the porcelain compositions that can be sintered at a low temperature of 960°C or lower.
A two-component composition comprising: However, the above-mentioned two-component composition has a high dielectric loss and a low specific resistance, and further improvement has been desired. Therefore, Pb is used as the third component.
A proposal has been made to improve the above-mentioned drawbacks by adding (Mn _2/3 W _1/3 )O ₃ (Japanese Patent Laid-Open No. 55-23058). However, the above Pb(Fe _2/3 W _1/3 )O ₃ −PbZrO ₃
and Pb(Mn _2/3 W _1/3 ) O ₃ added to it, the porcelain has a low bending strength, and its use as a ceramic composition for multilayer capacitors must be limited to a narrow range. I didn't get it. In view of the above points, the present invention can be sintered at a temperature of 960°C or less, has high mechanical strength, high specific resistance, high dielectric constant, good temperature change rate of dielectric constant, and has dielectric loss. This provides a small porcelain composition. That is, the present invention uses iron-lead tungstate [Pb
(Fe _2/3 W _1/3 )O ₃ ], lead zirconate [PbZrO ₃ ] and lead manganese antimonate [Pb(Mn _1/3 Sb _2/3 )
_{A ternary composition consisting of [Pb(Fe 2/3 W 1/3} )
When expressed as O ₃ ] x [ PbZrO ₃ ] y [ Pb (Mn _1/3 Sb _2/3 ) O ₃ ] z (where x + y + z = 1.000), the compounding ratios x, y, and z are each 0.500≦x ≦0.800,
It is characterized by being in the range of 0.150≦y≦0.498 and 0.002≦z≦0.050. The present invention will be explained in detail below with reference to Examples. Using sharp oxide (PbO), iron oxide (Fe ₂ O ₃ ), tungsten oxide (WO ₃ ), zirconium oxide (ZrO ₂ ), antimony oxide (Sb ₂ O ₃ ) and manganese carbonate (MnCO ₃ ) as starting materials, Weigh according to the mixing ratio shown in the table. Note that MnCO ₃ was converted into MnO to obtain the required amount. Next, after wet mixing in a ball mill, pre-baking at 700-800℃, then
It was pressure-molded into a disc shape with a diameter of 16 mm and a thickness of about 10 mm at a pressure of 0.7 ton/Km ² and sintered at 880°C to 950°C. The obtained sintered body was cut into 4 discs with a thickness of 1 mm.
Five 0.5 mm disks were obtained. Silver electrodes were baked on both sides of a 1 mm thick disk at 600°C to evaluate the electrical characteristics.
The dielectric constant and dielectric loss were measured at a frequency of 1kHz and a temperature of 20℃. Insulation resistance was measured by applying a voltage of 50V and after 1 minute at a temperature of 20°C. Regarding the temperature characteristics, the rate of change in capacity at +85°C was determined based on the room temperature of 20°C. 0.5 mm to evaluate mechanical properties by bending strength
A rectangular plate with a width of 2 mm and a length of about 13 mm was cut out from the disk. Determine the breaking load using the three-point method with a distance between fulcrums of 9 mm.
Pm [Kg] was measured, and the bending strength was determined using the formula: τ=3/2Pml/Wt ² [Kg/cm ² ]. Here, l is the distance between the supporting points, t is the thickness of the sample, and w is the width of the sample. Electrical properties are average values of 4 samples, bending strength is sample 10
It was calculated from the average value of the points. The relationship between the blending ratio and various properties of the porcelain thus obtained is shown in the following table.

【table】

[Table] As is clear from the results shown in the table, the present invention
Pb(Fe _2/3 W _1/3 )O ₃ −PbZrO ₃ −Pb(Mn _1/3 Sb _2/3 )
The three-component porcelain composition consisting of O ₃ can be sintered at a low temperature of 960°C or lower, and has higher bending strength and higher specific resistance than Pb(Fe _2/3 W _1/3 ) O ₃ −PbZrO ₃ . , low dielectric loss. Moreover, the temperature change rate of dielectric constant is also good.
It can be seen that an excellent ceramic composition for multilayer capacitors with high practicality can be obtained by the present invention. Note that the composition of the present invention [Pb(Fe _2/3 W _1/3 ) O ₃ ]
When expressed as x[PbZrO ₃ ]y[Pb(Mn _1/3 Sb _2/3 )O ₃ ]z, x, y, and z are each 0.50≦x≦
0.80, 0.15≦y≦0.498, 0.002≦z≦0.05 (however, x+y+z=1.000). x<
0.50 and y>0.50, the Curie temperature shifts to a higher temperature side than room temperature, and when x>0.80 and y<0.15, the Curie temperature shifts to a lower temperature side more than room temperature, and in both cases, the dielectric constant at room temperature decreases. When z<0.002, the bending strength is small, and when z>0.05, the specific resistance is small. For the above reasons, the composition is limited to the above composition range.

Claims (1)

[Claims] 1. Iron/lead tungstate [Pb (Fe _2/3 W _1/3 )
_{[ Pb ( Fe 2/3 W 1/3} ) _O3 ]x[ _PbZrO3 ]y[Pb(Mn _1/3
Sb _2/3 ) O ₃ ] When expressed as z (however, x + y +
z=1.000) A porcelain composition characterized in that the mixing ratios X, Y, and Z are in the following ranges: 0.500≦x≦0.800, 0.150≦y≦0.498, and 0.002≦z≦0.050.