JPH06231993A - Grain boundary insulating semiconductor ceramic composition - Google Patents

Abstract

PURPOSE:To provide excellent characteristics such as capacitance, apparent dielectric constant, a dielectric loss, a capacitance temperature characteristic, or the like and reduce variations in the characteristics of each product by a method wherein a formula (Sr(1-x)Cax)zTi(1-y)NbyO3 is a main component, which includes specified Cu, Si. CONSTITUTION:A main component is a formula (Sr(1-x)Cax)zTi(1-y)NbyO3 (x, y, z are respectively x=0.025 to 0.08, y=0.004 to 0.01, z=0.992 to 0.998). For this main component 100g, Cu is converted into CuO of which 0.005 to 0.1g is included, and Si is converted into SiO2 of which 0.01 to 0.08g is included to obtain a grain boundary insulating semiconductor ceramic composition. Thus, it is possible to provide a grain boundary insulating semiconductor ceramic capacitor having excellent characteristics such as higher capacitance and specific inductive capacity, smaller variations of capacitance, a smaller dielectric loss, and a capacitance temperature characteristic + or -10% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grain boundary insulating semiconductor porcelain composition, and more specifically, it has a large capacity of strontium titanate as a main component and excellent capacitance-temperature characteristics, and the capacitance of each product is The present invention relates to a grain boundary insulation type semiconductor ceramic composition having little variation.

[0002]

2. Description of the Related Art Generally, a grain boundary insulation type semiconductor ceramic capacitor is known as a capacitor which can obtain a very large effective capacitance because only a grain boundary portion is used as a dielectric. Strontium titanate (SrTiO ₃ ), barium titanate (BaTiO ₃ ), magnesium titanate (MgTi
O ₃ ), calcium titanate (CaTi0 ₃ ), lead titanate (Pb
It is known that various compounds are added to components such as TiO ₃ ) or the main component is a composition obtained by mixing the components.

Regarding the characteristics of the grain boundary insulation type semiconductor ceramic capacitor, for example, the grain boundary insulation type using, as a constituent material, barium titanate (BaTiO ₃ ) as a main component and dysprosium oxide (Dy ₂ O ₃ ) is added. In the semiconductor porcelain capacitor, the maximum effective relative permittivity (ε _S ) shows a large value of 40,000 to 50,000, while its capacitance temperature characteristic (TC value) is −30 with the capacitance at 20 ° C. as a reference value. ℃
When the maximum rate of change with respect to the reference capacitance in the temperature range of to + 85 ° C is taken, the value is as large as ± 40%, and the dielectric loss (tan δ) is as large as about 5%. It was

Further, the main component of the semiconductor porcelain composition is strontium titanate (SrTiO ₃ ), and the grain boundary insulation type semiconductor porcelain capacitor to which dysprosium oxide (Dy ₂ O ₃ ) or cerium dioxide (CeO ₃ ) is added has a maximum Although the effective relative permittivity (ε _S ) is as low as about 30,000, the capacitance-temperature characteristic (T
C value is improved to about ± 20%, and dielectric loss (ta
It was found that n δ) was also improved to about 2 to 3%.

As a capacitor, generally, the capacitance and the apparent relative permittivity (ε _app ) related thereto are sufficiently high, and the dielectric loss (tan δ) and the temperature characteristic of capacitance (TC value) are sufficient. It is necessary to be small.

As in the above-mentioned known example, the strontium titanate (SrTiO ₃ ) based grain boundary insulating semiconductor ceramics generally have an apparent relative dielectric constant (ε) in comparison with barium titanate (BaTiO ₃ ) based ones. _App ) is slightly inferior, but it is used in various applications due to its excellent dielectric loss (tan δ), capacitance temperature characteristic (TC value), high frequency characteristic, etc., and various sintering aids or diffusing substances were added. It is being studied by the system.

An example of a method for producing a conventionally used strontium titanate (SrTiO ₃ ) based grain boundary insulating semiconductor ceramic composition will be described. First, strontium titanate (Sr
TiO ₃ ) as a main raw material, niobium pentoxide (Nb ₂ O ₅ ), yttrium oxide (Y ₂ O ₃ ) etc. are added to this as a valence control aid, and silicon oxide (SiO ₂ ) is used as a sintering aid. ₂ ), aluminum oxide (Al ₂ O ₃ ), manganese oxide (MnO ₂ ), cupric oxide (CuO), etc. are added in one kind or in a combination, and sintered in a reducing atmosphere to form a semiconductor ceramic composition. Get things. Next, bismuth oxide (Bi ₂ O ₃ ), cupric oxide (CuO 2), in order to provide an insulating layer at the grain boundaries of this semiconductor porcelain composition,
A grain boundary insulating semiconductor porcelain composition is manufactured by thermally diffusing a metal oxide such as manganese oxide (MnO ₂ ).

[0008]

With the recent miniaturization of equipment, there is a demand for a capacitor having a larger capacity and a good capacitance temperature characteristic (TC value). Generally, as a method of increasing the electrostatic capacity of a grain boundary insulation type semiconductor ceramic capacitor and improving the temperature characteristic (TC value) of the electrostatic capacity, the crystal grains in the ceramic composition are increased and thermal diffusion to the crystal grain boundaries is performed. A method of increasing the amount of the metal oxide to be made and a method of lowering the temperature when thermally diffusing to the crystal grain boundaries are conceivable. However, when the crystal grains in the porcelain composition are increased to increase the amount of metal oxide to be thermally diffused or the thermal diffusion temperature is lowered, the metal oxide remains on the surface of the semiconductor porcelain during thermal diffusion. As a result, the temperature characteristic of capacitance (TC value) is deteriorated, the capacitance of each manufactured porcelain composition varies, and an abnormal value of dielectric loss (tan δ) is generated. There was a problem that it might occur.

[0009]

In view of the above-mentioned problems, the present inventors have found that strontium titanate contains calcium titanate in order to improve the capacitance-temperature characteristic (TC value) of the strontium titanate-based semiconductor ceramic composition. As a result of studying a system in which is dissolved, niobium pentoxide is used as a semiconductor agent,
In the grain boundary insulating type semiconductor porcelain composition in which a specific amount of silicon oxide and cupric oxide is added to this, the crystal grains grow uniformly during sintering, and the insulating agent is thermally diffused in the obtained semiconductor porcelain to form grains. By forming the field insulation layer, it has excellent characteristics such as capacitance, apparent relative permittivity (ε _app ), dielectric loss (tan δ) and capacitance temperature characteristic (TC value). It was found that a grain boundary insulating type semiconductor ceramic composition with less variation in the above can be obtained, and the present invention has been completed.

[0010] That is, the grain boundary insulation type semiconductor ceramic composition according to the present _{invention, (Sr (1-x)} Ca x) z Ti 1-y Nb y O 3 ( wherein, x,
y and z are x = 0.025 to 0.08 and y = 0.004 to 0, respectively.
01, a value in the range of z = 0.992 to 0.998) as a main component, and 0.005 to 0.1 when Cu is converted to CuO with respect to 100 g of the main component.
It is characterized by containing 0.01 to 0.08 g of g and Si converted to SiO ₂ .

In the present invention, the main component (Sr _{(1-x)
Ca x) z Ti 1-y} Nb y O 0 the value of x involved in the ratio of Sr and Ca in _3.
025 to 0.08 means that the capacitance temperature characteristic (TC value) is deteriorated when the value of x is less than 0.025, and the capacitance and the apparent dielectric constant are increased when the value of x exceeds 0.08. This is because the rate (ε _app ) becomes small.

The main component (Sr _(1-x) Ca _x ) _z Ti _1-y
Nb _y of _{O 3 (Sr (1-x} ) Ca x) as defined as the value of 0.992 to 0.998 of z related to the proportion of the Ti, the value of the z is 0.992
If it is less than the above range, the sinterability is deteriorated and it is not densified, and if the value of z exceeds 0.998, abnormal grain growth occurs and a dense sintered body cannot be obtained.

Further, the main component (Sr _(1-x) Ca _x ) _z Ti _1-y
The value of y related to the ratio of Nb to Ti of Nb _y O ₃ is 0.004 to 0.
The definition of 01 is that when the value of y is less than 0.004, the value of dielectric loss (tan δ) becomes large, and when the value of y is
This is because if it exceeds 0.01, the sinterability deteriorates and a dense sintered body cannot be obtained.

The content of Si based on 100 g of the main component is SiO ₂
The value of 0.01 to 0.08 g was calculated as follows: If the Si content per 100 g of the main component is less than 0.01 g in terms of SiO ₂ , the variation in capacitance between products will increase, and the Si This is because when the content exceeds 0.08 g in terms of SiO ₂ , the capacitance and the apparent relative permittivity (ε _app ) become small.

The content of Cu based on 100 g of the main component is 0.005 to 0.1 g in terms of CuO, which means that Cu based on 100 g of the main component is
If the content of Cu is less than 0.005g in terms of CuO, the variation in capacitance will increase, and if the content of Cu exceeds 0.1g in terms of CuO, abnormal grain growth will occur and This is because the temperature characteristic (TC value) of the capacitance is deteriorated without providing the above characteristics.

[0016]

According to the above structure, (Sr _(1-x) Ca _x ) _z Ti _1-y Nb
_Since the value of z in the main component composed of _y O ₃ is 0.992 to 0.998, Ti at the B site becomes excessive, lattice defects increase, and semiconductor formation is promoted. Further, the value of y in the main component is 0.00
Since it is 4 to 0.01, the semiconductor conversion is further promoted by controlling the valence. The value of x in the main component is 0.025 to 0.08.
Therefore, part of the A site is replaced by Ca, and abnormal grain growth is suppressed. Further, by containing SiO ₂ , sintering is promoted to form a dense sintered body and the crystal grains have a uniform size. Therefore, the obtained grain boundary insulating semiconductor ceramic composition according to the present invention has a capacitance, an apparent relative permittivity (ε _app ), a dielectric loss (tan δ), a capacitance temperature characteristic (TC value), etc. The above characteristics are excellent, and there is little variation in the characteristics of each product.

[0017]

EXAMPLES Examples and comparative examples of the grain boundary insulating semiconductor ceramic composition according to the present invention will be described below. First, the raw material powder of strontium carbonate (SrCO ₃ ) and calcium carbonate (CaCO ₃ ) with a purity of 99.9% or higher is used as a raw material and has a purity of 99.9%.
By adding the above titanium oxide (TiO ₂ ), (Sr _(1-x) Ca _x ) / Ti
The powder having the z value, which is the molar ratio of
% Or more niobium pentoxide (Nb ₂ O ₅ ), cupric oxide (CuO).
Also, various amounts of silicon oxide (SiO ₂ ) are added for the preparation. The mixing ratio of each raw material is shown in Tables 1 and 2 below. The compounding is performed by accurately weighing each raw material, wet mixing and pulverizing for about 20 hours by a ball mill or the like. This crushed powder is dried and then crushed, and in air, 1000-12
Calcination synthesis is performed for 2 hours in the temperature range of 00 ° C. It was confirmed by X-ray diffraction analysis, composition analysis, etc. that a predetermined solid solution was synthesized by the calcination synthesis.

Next, the calcined synthetic powder is crushed, sized and granulated, and then a pressure of 1.0 to 2.0 t / cm ² is applied to the crushed synthetic powder to obtain a diameter of 10 mm,
A disk-shaped molded body having a thickness of 0.8 mm is formed. This molded body is degreased by heat treatment in air at about 1000 ° C. for 2 hours, and further hydrogen 1 to 15 vol% and nitrogen 99 to 8
Baking is performed in the range of 1400 to 1450 ° C. for 4 to 8 hours in a reducing atmosphere of 5 vol%.

Regarding the composition of the obtained sintered body, the composition was analyzed by ICP analysis or the like after dissolving the sintered body with an acid or the like, and it was confirmed that the composition was the same as that of the prepared raw material.

Next, the obtained sintered body was thoroughly washed with an organic solvent and hot water, and then bismuth oxide (Bi ₂ O ₃ ) and cupric oxide (CuO 2) (CuO) were used as diffusion materials on one surface of the sintered body. ), Sodium carbonate (Na ₂ CO ₃ ) or sodium oxide (Na ₂ O), at least one metal oxide paste is applied,
In the air, it is heated in the range of 1050 to 1200 ° C. for 1 to 2 hours for thermal diffusion to obtain an insulating grain boundary type semiconductor ceramic composition. Finally, a silver paste is printed on both sides of the thus-obtained insulating grain boundary type semiconductor porcelain composition and baked at 800 ° C. for about 2 hours to form a silver electrode to obtain a semiconductor porcelain capacitor.

Evaluation of various electrical characteristics of the obtained conductor ceramic capacitor was carried out as follows.

The capacitance, the dielectric loss (tan δ) and the apparent relative permittivity (ε _app ) were measured with an impedance analyzer at a frequency of 1 KHz and a measurement voltage of 1 V, and the capacitance-temperature characteristic (TC value) Was evaluated by the rate of change of the capacitance measured at −25 ° C. and + 85 ° C. with reference to the capacitance measured at 20 ° C. Capacitance variation (3c
V) is a value expressed by the following mathematical formula 1, and the capacitance is measured for 50 semiconductor ceramic capacitors manufactured under the same conditions, and the standard deviation (σ) and the average value (σ) obtained from these values are measured. ξ) is used.

[0023]

## EQU00001 ## Capacitance variation (3 cV) = 3.times..sigma..xi. (Where, .sigma. Standard deviation, .xi .: average value) In Table 1, the sample numbers are marked with * in the present invention. The present invention relates to comparative examples outside the range, and the others relate to examples within the scope of the present invention.

[0024]

[Table 1]

[0025]

[Table 2]

The following can be seen from the data of the comparative examples in Tables 1 and 2. The value of x is less than 0.025 0.01, 0.02
The variation in capacitance temperature characteristics (TC value) and the capacitance increase, and the capacitance decreases when the value of x exceeds 0.08 and becomes 0.10. When the value of y becomes 0.002 which is smaller than 0.004, the value of dielectric loss (tan δ) becomes large,
The variation in capacitance also increases. When the z value is 0.990, which is smaller than 0.992, the sinterability deteriorates and a dense sintered body cannot be obtained, so that the electrical characteristics cannot be measured and the z value is 0.
The capacitance becomes smaller at 1.000, which exceeds 998. In addition, when CuO was not contained, the variation in capacitance increased, and the content of CuO exceeded 0.1 g per 100 g of the main component.
If it is 0.15g or 0.2g, the insulation will be poor. Further if not containing SiO ₂ becomes large variation in capacitance, SiO ₂
The content of 0.10g that exceeds 0.08g for 100g of the main component
The capacitance becomes smaller at 0.12g.

On the other hand, in the grain boundary insulating semiconductor ceramic composition according to the example, the capacitance and the apparent relative permittivity (ε _app ) are large, the variation in the capacitance is small, and the dielectric loss is small. (Tan δ) is small, and the capacitance-temperature characteristic (T
The C value) is within ± 10%, which is excellent in each characteristic.

[0028]

As described above in detail, in the grain boundary insulating semiconductor ceramic composition according to the present invention, (Sr _(1-x) Ca _x ) _z Ti
_1-y Nb _y O ₃ (where x, y, and z are respectively x = 0.025
.About.0.08, y = 0.004 to 0.01, z = 0.992 to 0.998) as the main component, and Cu is CuO for 100 g of the main component.
Converted to 0.005 to 0.1 g, and Si converted to SiO ₂ 0.01 to 0.
Since it contains 08g, the capacitance and apparent relative permittivity (ε _app ) are large, the variation in capacitance is small, the dielectric loss (tan δ) is small, and the capacitance temperature characteristic (T
It is possible to provide a grain boundary insulation type semiconductor ceramic capacitor having excellent C-values within ± 10%.

Claims (1)

[Claims] [Claim 1] _{(Sr (1-x) Ca} x) z Ti 1-y Nb y O 3 ( wherein, x,
y and z are x = 0.025 to 0.08 and y = 0.004 to 0, respectively.
01, a value in the range of z = 0.992 to 0.998) as a main component, and 0.005 to 0.1 when Cu is converted to CuO with respect to 100 g of the main component.
A grain boundary insulating semiconductor porcelain composition containing 0.01 to 0.08 g of g and Si in terms of SiO ₂ .