JPH0127016B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a porcelain composition, particularly a porcelain composition having a high dielectric constant, a low sintering temperature, and high mechanical strength. It is well known that porcelain containing barium titanate (BaTiO ₃ ) as a main component has been widely put into practical use as a high dielectric constant ceramic composition. However, for products whose main component is barium titanate (BaTiO ₃ ), the sintering temperature is usually 1300 to 1400℃.
The temperature is high. Therefore, when this is used in a multilayer capacitor, a material that can withstand this sintering temperature must be used for the internal electrodes, such as an expensive noble metal such as platinum or palladium, resulting in high manufacturing costs. There is. In order to make multilayer capacitors cheaply, it is necessary to use porcelain that can be sintered at as low a temperature as possible, especially below 1000°C, so that inexpensive metals such as silver and nickel can be used for the internal electrodes. In addition, in the case of chip capacitors, when the 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 porcelain that makes up the chip capacitor, causing cracks to the chip capacitor. occurs or
It may be damaged. Furthermore, in the case of a dip capacitor coated with epoxy resin or the like, cracks may occur in the dip capacitor due to the stress of the coating resin. In either case, the lower the mechanical strength of the porcelain forming the capacitor, the more likely it is to crack and break, resulting in lower reliability. Therefore, it is of practical importance to increase the mechanical strength of porcelain as much as possible. By the way, Pb(Fe _2/3 W _1/3 ) O ₃ - is one of the porcelain compositions that can be sintered at a low temperature of 1000℃ or less.
Two-component compositions consisting of PbZrO ₃ have already been proposed. 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 (Mn _2/3 W _1/3 ) is used as the third component.
Attempts have been made to improve the above drawbacks by adding O ₃ and the like (Japanese Patent Application 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 and the like have low bending strength, and their use as ceramic compositions for multilayer capacitors has had to be limited to a narrow range. In view of the above points, the present invention can be sintered at a temperature of 1000℃ or less, has high mechanical strength, has a high dielectric constant, has a good temperature change rate of dielectric constant, has low dielectric loss, and has low specific resistance. The aim is to provide _a material that maintains the excellent characteristics of high performance, is highly reliable, _{and is} highly suitable for mass production. A two-component composition consisting of lead zirconate [PbZrO ₃ ] [Pb (Fe _2/3
W _1/3 ) O ₃ ] _x [PbZrO ₃ ] When expressed as _1-x , x is
At least one or more of niobium (Nb), tantalum (Ta), and antimony (Sb) is selected as a subcomponent to the main component composition in the range of 0.50≦x≦0.80, and the element is added to the main component by 0.02~ It is characterized by containing 2 atomic % of the additive. The present invention will be explained in detail below with reference to Examples. As starting materials, lead oxide (PbO), iron oxide (Fe ₂ O ₃ ), tungsten oxide (WO ₃ ), zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), tantalum oxide (Ta ₂ O ₅ ) and antimony oxide (Sb ₂ O ₃ ), and weigh them to the compounding ratio shown in the table. Then after wet mixing in a ball mill 700~800
Pre-fired at ℃ and then heated to a diameter of 16 mm at a pressure of 0.7 ton/cm ^2.
Pressure molded into a cylindrical shape with a thickness of 800 to 950 mm.
Sintered at °C. The obtained sintered body was cut to a thickness of 1
Four disks of mm diameter and five disks of 0.5 mm thickness were obtained. Silver electrodes were baked on both sides of a 1 mm thick disk to evaluate its electrical characteristics. Dielectric constant and dielectric loss at frequency 1K
Measured at Hz and temperature of 20°C. The specific resistance was measured by applying a DC voltage of 50 V and after 1 minute at a temperature of 20°C. Regarding temperature characteristics, the capacitance change rate 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. The distance between the supporting points was set to 9 mm, and the breaking load Pm [Kg] was measured using the three-point method, and τ = 3/2 Pml/wt ² [Kg/cm ²
] The bending strength τ [Kg/cm ² ] was determined according to the following formula.
However, l is the distance between the supporting points, t is the thickness of the sample, and w is the width of the sample. The electrical properties were determined from the average value of 4 samples, and the bending strength was determined from the average value of 10 samples. The relationship between the blending ratio and various properties of the porcelain thus obtained is shown in the following table.

【table】

【table】

[Table] As is clear from the results shown in the table, a two-component composition consisting of iron/lead tungstate [Pb (Fe _2/3 W _1/3 ) O ₃ ] and lead zirconate [PbZrO ₃ ] was
(Fe _2/3 W _1/3 ) O ₃ ] _x [PbZrO ₃ ] Niobium (Nb) is added as a subcomponent to the main component composition where x is within the range of 0.50≦x≦0.80 when expressed as _1-x . , tantalum (Ta)
and antimony (Sb), and select the element from 0.02 to 0.02 to the main component.
By adding 2 atomic percent, it has a high dielectric constant, good temperature characteristics, low dielectric loss, high specific resistance, and high bending strength.It has excellent properties and is highly reliable and practical. It can be seen that an excellent high dielectric constant ceramic composition rich in porcelain compositions can be obtained. The porcelain of the present invention, which exhibits such excellent properties, has a low temperature of 1000° C. or less, and therefore has the extremely excellent effect of making it possible to reduce the cost of internal electrodes of multilayer capacitors. Note that compositions in which the blending ratio x of the main components is less than 0.5 or more than 0.8 are not practical because the Curie point deviates significantly toward higher or lower temperatures than the practical temperature range, resulting in a low dielectric constant at room temperature. Furthermore, if the amount of one or more of the subcomponents Nb, Ta, and Sb is less than 0.02 atom%, the effect of improving the bending strength will be small, and if it exceeds 2 atom%, the dielectric loss will increase, making it impractical. .

Claims (1)

[Claims] 1. Iron/lead tungstate [Pb (Fe _2/3 W _1/3 ) O ₃ ]
A two-component composition consisting of lead zirconate and lead zirconate [PbZrO ₃ ] is expressed as [Pb (Fe _2/3 W _1/3 ) O ₃ ] _x [PbZrO ₃ ] _1-x , where x is 0.50≦x≦0.80. At least one or more elements selected from niobium (Nb), tantalum (Ta), and antimony (Sb) as a subcomponent are added to the main component composition within the range of 0.02 to 2 atomic percent relative to the main component. A porcelain composition characterized by: