JPH0419646B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a porcelain composition, particularly a porcelain composition that can be sintered at a low temperature of 1100° C. or lower, has a high dielectric constant, has a high insulation resistance at room temperature and high temperature, and has high mechanical strength. It is well known that ceramics containing barium titanate (BaTiO ₃ ) as a main component have been widely put into practical use as dielectric ceramic compositions. However, those whose main component is barium titanate (BaTiO ₃ ) have a sintering temperature of usually 1300 to 1400°C. Therefore, when using this material 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, which has the disadvantage of high manufacturing costs. be. In order to make multilayer capacitors cheaply, it is necessary to use inexpensive metals mainly composed of silver, nickel, etc., which can be used for the internal electrodes.
Porcelain that can be sintered at as low a temperature as possible, especially below 1100°C, is needed. Furthermore, the electrical properties of the ceramic composition are basically required to have a high dielectric constant, low dielectric loss, and high insulation resistance. Furthermore, regarding the value of insulation resistance, MIL-C-55681B, the Military Specification, which is a US Department of Defense standard that requires highly reliable components.
In order to obtain a highly reliable ceramic capacitor, not only the value at room temperature but also the value at 125°C is specified, the insulation resistance must be high not only at room temperature but also at the maximum operating temperature. It is necessary to take In addition, in the case of multilayer 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. This may cause cracks or damage. Furthermore, even in the case of dip capacitors 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 easier 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(Mg _1/2 W _1/2 ) O ₃ -PbTiO ₃ based ceramic composition has already been reported in N:N. Krajnik, A. Ai. Maglanovskaya NNKrainik and
AIAgrarovskaya (Fiziko Tverdogo Tela,
(Sr _x Pb _1-x TiO ₃ ) _a (PbMg _0.5 W _0.5 O ₃ ) _b
[However, x = 0 to 0.10, a is 0.35 to 0.5, b is 0.5
~0.65, and a+b=1] is disclosed in JP-A-52-21662 as a monolithic capacitor and its manufacturing method, and as a dielectric powder composition in JP-A-52-21699. ing. However, none of them discloses specific resistance at all, and the practicality of these ceramic compositions was not clear. In addition, the inventors have already found that Pb can be sintered at a temperature of 910-950℃.
It consists of a two-component system of (Mg _1/2 W _1/2 )O ₃ and PbTiO ₃ and is expressed as [Pb(Mg _1/2 W _1/2 )O ₃ ] _x [PbTiO ₃ ] _1-x. Sometimes compositions are proposed in which x is in the range 0.65<x≦1.00. This composition has a high product of dielectric constant and specific resistance, and has excellent electrical properties with low dielectric loss. However, since all of the above compositions have low mechanical strength, their applications have had to be limited to a narrow range. Furthermore, regarding the ternary system including the Pb(Mg _1/2 W _1/2 )O ₃ -PbTiO ₃ system, Japanese Patent Application Laid-Open No. 111011/1983
Pb(Mg _1/2 W _1/2 )O ₃ −PbTiO ₃ −Pb(Mg _1/3 Nb _2/3 )
The O ₃ system was developed as Pb (Mg _1/2
W _1/2 )O ₃ −PbTiO ₃ −Pb(Mg _1/3 Ta _2/3 )O ₃ system is
Each is disclosed. However, none of them discloses specific resistance or mechanical strength, and the practicality of these magnetic compositions was not clear. In addition, the present inventors have already discovered that Pb(Mg _1/2 W _1/2 )O ₃ −
A ternary composition of _PbTiO3 -Pb(In1 _/ 2Nb1 _/2 ) _O3 has already been proposed. This composition can be sintered in the low temperature range of 900 to 1100°C, has excellent properties such as high dielectric constant, low dielectric loss, and high insulation resistance at room temperature and high temperature. However, since this composition has low mechanical strength, its use has had to be limited to a narrow range. In view of the above points, the object of the present invention is to
A highly reliable porcelain that can be sintered at a low temperature of 1100℃, has excellent electrical properties such as high dielectric constant, low dielectric loss, and high insulation resistance at room and high temperatures, and also has high mechanical strength. It is intended to provide a composition. According to the present invention, magnesium lead tungstate [Pb (Mg _1/2 W _1/2 ) O ₃ ], lead titanate [PbTiO ₃ ]
and indium lead niobate [Pb (In _1/2 Nb _1/2 )
A _three -component composition consisting of [Pb (Mg _1/2 W _1/2 )
When expressed as O ₃ ] _x [PbTiO ₃ ] _y [Pb(In _1/2 Nb _1/2 ) O ₃ ] _z (where x+y+z=1.00), the following composition point (x =0.796, y=0.199, z=0.005) (x=0.48, y=0.12, z=0.40) (x=0.21, y=0.09, z=0.70) (x=0.12, y=0.18, z=0.70) (x = 0.398, y = 0.597, z = 0.005) and the composition range surrounded by these five points, manganese lead niobate [Pb (Mn _1/3 A porcelain composition characterized in that it contains 0.05 to 6 mol % of Nb _2/3 ) O ₃ based on the main component is obtained. The present invention will be explained in detail below with reference to Examples. Lead oxide (PbO) with a purity of over 99.9% as a starting material,
Using magnesium oxide (MgO), tungsten oxide (WO ₃ ), titanium oxide (TiO ₂ ), indium oxide (In ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ), and manganese carbonate (MnCO ₃ ), the table Weigh each to achieve the mixing ratio shown in . Next, the weighed materials were wet-mixed in a ball mill, pre-baked at 750-800°C, pulverized in this powder ball mill, separated into powders,
After drying, add an organic binder, size the particles and press them to form 4 discs with a diameter of 16 mm and a thickness of about 2 mm, and a diameter of 16 mm.
A cylinder with a thickness of about 10 mm was created. Next, samples with the composition range of the present invention were tested at a temperature of 900 to 1100℃ in air.
Sintered for hours. 600 on the top and bottom surfaces of four sintered disks.
The silver electrode was baked at ℃, and the capacitance and dielectric loss were measured using a digital LCR meter at a frequency of 1 KHz, a voltage of 1 Vr.ms, and a temperature of 20 ℃, and the dielectric constant was calculated. Next, a voltage of 50V was applied for 1 minute using a super insulation resistance meter, insulation resistance was measured at temperatures of 20°C and 125°C, and specific resistance was calculated. In order to evaluate the mechanical properties in terms of bending strength, 10 rectangular plates with a thickness of 0.5 mm, a width of 2 mm, and a length of approximately 13 mm were cut out from the sintered cylinder. The distance between the fulcrums was set to 9 mm, and the breaking load Pm [Kg] was measured using the two-point method, and τ =
The bending strength τ [Kg/cm ² ] was determined according to the formula 3/2Pml/Wt ² [Kg/cm ² ]. However, l is the distance between the fulcrums,
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 disk samples, and the bending strength was determined from the average value of 10 rectangular plate samples. The main component of the porcelain obtained in this way [Pb (Mg _1/2 W _1/2 ) O ₃ ] _x
[PbTiO ₃ ] _y [Pb (In _1/2 Nb _1/2 ) O ₃ ] ₄ blending ratio x,
y, z and subcomponent addition amount, dielectric constant, dielectric loss,
The relationship between specific resistance and bending strength at 20°C and 125°C is shown in the table below.

【table】

[Table] As is clear from the results shown in the table, according to the present invention, the dielectric constant is as high as 1010 to 3670, and the dielectric loss is 0.4.
It is small at ~2.9%, and the specific resistance is 2.3× at 20℃
It has a high value of 10 ¹² to 7.6×10 ¹³ Ω・cm, and even at 125°C, it shows a high value of 1.2×10 ¹¹ to 1.1×10 ¹³ Ω・cm, and the bending strength is 1030 to 1470 Kg/cm ² , which is a practical value. A highly reliable and extremely practical ceramic composition exhibiting a sufficiently high value can be obtained. The porcelain composition of the present invention, which exhibits such excellent properties, has a low sintering temperature of 1,100°C or less, which makes it possible to reduce the cost of internal electrodes in multilayer capacitors, as well as save energy and furnace materials. Very good effects also occur. In addition, in the main component composition range, the resistivity at high temperatures becomes small outside the line connecting composition points 2 and 15, making it impractical. Composition points 15, 16,
Outside the line connecting 17, 3, and 2, the dielectric constant becomes small and is not practical. In addition, Pb (Mn _1/3
If the amount of Nb _2/3 ) O ₃ added is less than 0.05 mol %, the effect of improving the bending strength is small, and if it exceeds 6 mol %, the bending strength decreases, which is not practical. The figure shows the composition range of the main components of the present invention. The numbers shown in the figure correspond to the numbers of the main component blending ratios shown in the table.

[Brief explanation of drawings]

The figure is a diagram showing the main component composition range of the present invention and the composition points shown in Examples.

Claims (1)

[Claims] 1. Magnesium lead tungstate [Pb
(Mg _1/2 W _1/2 ) O ₃ ], lead titanate [PbTiO ₃ ] and lead indium niobate [Pb (In _1/2 Nb _1/2 ) O ₃ ]
A three-component composition consisting of [Pb(Mg _1/2 W _1/2 ) O ₃ ] _x
When expressed as [PbTiO ₃ ] _y [Pb (In _1/2 Nb _1/2 ) O ₃ ] _z (however, x+y+z=1.00), the following composition points on this ternary composition diagram (x=0.796, y=0.199, z=0.005) (x=0.48, y=0.12, z=0.40) (x=0.21, y=0.09, z=0.70) (x=0.12, y=0.18, z=0.70) (x= 0.398, y=0.597, z=0.005) and in the composition range surrounded by these five points, manganese/lead niobate [Pb (Mn _1/3 Nb _2/3 ) is added as a subcomponent to the main component composition. A porcelain composition characterized in that it contains 0.05 to 6 mol% of O ₃ ] based on the main component.