JPH0127015B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a ceramic composition, particularly a ceramic composition with a high dielectric constant and a low sintering temperature. It is well known that as a conventional high permittivity dielectric material, a material containing barium titanate [BaTiO ₃ ] as a main component has been widely put into practical use. However, the sintering temperature of products whose main component is BaTiO ₃ is usually between 1300°C and 1400°C, and especially in the case of multilayer capacitors, internal electrodes whose main component is platinum or This method has the disadvantage of requiring the use of expensive noble metals such as palladium. 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 1000° C. or lower. An object of the present invention is to provide a composition that can be sintered at a temperature of 1000°C or lower, has 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 ceramic, which can cause minute cracks or, in severe cases, damage to the chip capacitor. There are cases where this happens. 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 is to crack, break, and become less reliable. Therefore, it is extremely important in practice to increase the mechanical strength of ceramics as much as possible. By the way, Pb(Fe2/3W1/3)O ₃ - is one of the porcelain compositions that can be sintered at low temperatures below 1000℃.
Two-component compositions consisting of PbZrO ₃ have already been proposed. However, the above two-component composition has a high dielectric loss and a low specific resistance, and further improvement has been desired. Therefore, the third component is Pb (Mn2/
3W1/3) A proposal has been made to improve the above drawbacks by adding O ₃ etc. (Japanese Patent Laid-Open No. 55-23058). However, both the above-mentioned Pb(Fe2/3W1/3)O ₃ -PbZrO ₃ and those to which Pb(Mn2/3W1/3)O ₃ etc. are added have low bending strength of porcelain, and are not suitable as compositions for multilayer capacitors. had no choice but to limit its use to a narrow range. The present invention is composed of Pb(Fe2/3W1/3)O ₃ , PbZrO ₃ and Pb(Zn1/3Nb2/3)O ₃ and has improved all the above-mentioned drawbacks. That is, the ternary system of the present invention is [Pb(Fe2/3W1/3)O _{3 ]}
When expressed as [PbZrO ₃ ] _Y (Pb(Zn1/3Nb2/3)O ₃ ] _Z (however, X+Y+Z=1.00), the compounding ratios X, Y, and Z in this ternary composition diagram (X=
0.792, Y=0.198, Z=0.01), (X=0.40, Y=
0.10, Z=0.50), (X=0.25, Y=0.25, Z=
0.50) and (X=0.495, Y=0.495, Z=0.01)
It is characterized by being located on the line connecting the four composition points of The present invention provides a material that maintains excellent properties such as a good rate of change, low dielectric loss, and high specific resistance, is highly reliable, and is easily mass-produced. The present invention will be explained in detail below with reference to Examples. Lead oxide (PbO), iron oxide (Fe ₂ O ₃ ), tungsten oxide (WO ₃ ), zirconium oxide (ZrO ₂ ), niobium oxide (Nb ₂ O ₅ ), and zinc oxide are used as starting materials, and the specified Weigh according to the mixing ratio. Next, after wet mixing in a ball sill, pre-baking at 700℃~800℃, then under a pressure of 0.7ton/ ^cm2 ,
Pressure molded into a cylindrical shape with a thickness of about 10 mm and heated at 800℃ to 950℃
Sintered with The obtained sintered body was cut into four 1 mm disks.
Five 0.5 mm disks were obtained. Silver electrodes were baked on both sides of a 1 mm disk to evaluate the electrical characteristics. The dielectric constant and dielectric loss were measured at a frequency of 1 kHz and a temperature of 20°C.
For insulation resistance, apply a voltage of 50V, and after 1 minute, the temperature will decrease to 20V.
Measured at °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: γ=3Pml/2Wt ² [Kg/cm ² ]. However, l is the distance between the supporting points, t is the thickness of the sample, and W is the width of the sample.

【table】

[Table] Electrical properties were determined from the average value of 4 samples, and 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 table and FIGS. 1 to 6. The horizontal axis in the figure is Pb (Zn1/3Nb2/
3) The mole fraction of O ₃ or PbZrO ₃ is shown, and the sample number in the table is clearly indicated in the part corresponding to the composition shown in the table. Further, in the figure, curve a shows the dielectric constant, b shows the dielectric loss, c shows the specific resistance, d shows the temperature characteristic, and e shows the bending strength. As is clear from this result, the Pb of the present invention
(Fe2/3W1/3)O ₃ ―PbZrO ₃ ―Pb(Zn1/
The ternary porcelain consisting of 3Nb2/3) _O3 can be sintered at low temperatures below 1000℃, has a high dielectric constant, good temperature characteristics, low dielectric loss, high specific resistance,
High bending strength. In other words, it has excellent properties,
It can be seen that a highly reliable high dielectric constant ceramic composition for horizontal layer capacitors can be obtained. The composition of the present invention is [Pb(Fe2/3W1/3)
When expressed as O ₃ ] _X [PbZrO ₃ ] _Y [Pb(Zn1/3Nb2/3)O ₃ ] _Z , as shown in Figure 7, =
0.792, Y=0.198, Z=0.01), (X=0.40, Y=
0.10, Z=0.50), (X=0.25, Y=0.25, Z=
0.50) and (X=0.495, Y=0.495, Z=0.01)
It is limited to the line connecting the four composition points and within the range of this line. Note that the numbers 1 to 25 in FIG. 7 indicate the sample numbers shown in the table. The Curie temperature is lower than the practical temperature range in the range of X>0.792 and the part where Y<0.2 is outside the range of the present invention, and the Kyrie temperature is lower than the practical temperature range in the range of X<0.25 and the part where Y>0.25 is outside the range of the present invention. The dielectric constant at room temperature decreases in both cases. On the other hand Z
When it is <0.01, the bending strength becomes low, the specific resistance decreases, and the dielectric loss increases. When Z>0.50, the dielectric loss becomes large. For the above reasons, the composition is limited to the above composition range.

[Brief explanation of drawings]

FIG. 1 to FIG. 6 are diagrams showing the relationship between each composition in the table and its characteristics. In the curve in the figure, a is the dielectric constant, b is the dielectric loss, c is the specific resistance, d is the temperature change,
e indicates the characteristic of bending strength. 7th
The figure shows the composition range of the present invention and the composition points of the compounding ratios shown in the examples.

Claims (1)

[Claims] 1. Iron/lead tungstate [Pb (Fe2/3W1/3)
A ternary composition consisting of lead zirconate [PbZrO ₃ ], lead zirconate [PbZrO 3 ], and zinc-lead niobate [Pb(Zn1/3Nb2 _/ 3)O ₃ ] (Pb(Fe2/3W1/3)O _{3 )}
[PbZrO ₃ ] _Y (Pb(Zn1/3Nb2/3)O ₃ ) When expressed as _Z (X+Y+Z=1.00), in this three-component composition diagram, the compounding ratios X, Y, and Z are respectively (X=0.792, Y=0.198, Z=0.01), (X=0.40,
Y=0.10, Z=0.50), (X=0.25, Y=0.25, Z
=0.50) and (X=0.495, Y=0.495, Z=0.01)
A porcelain composition characterized by being located within a region surrounded by a line connecting four composition points (including on the line).