JPH06310363A - Semiconductor ceramic and manufacture thereof - Google Patents

Abstract

PURPOSE:To porvide a semiconductor ceramic with high dielectric breakdown strength by a method wherein (Sr1-xCax)TiyO2y+1, at least a metal oxide selected out of CeO2, La2O3,WO3, Y2O3, and Nb2O5, and vanadium oxide are contained in the semiconductor ceramic. CONSTITUTION:Semiconductor ceramic contains 99.200 to 99.915mol% of (Sr1-xCax)TiyO2y+1 (x=0.31 to 0.52, y=0.99 to 1.01) as a first component. At least 0.075 to 0.600mol% fo metal oxide selected out of CeO2, La2O3, WO3, Y2O3, and Nb2O5 is contained as a second component. 0.01 to 0.20mol% of vanadium oxide is contained as a third component. Mixture of a first, a second, and a third component is molded into a prescribed shape, and the molded body is burned in an non-oxidizing atmosphere into a sintered body. The sintered body is thermally treated in an oxidizing atmosphere for the formation of a semiconductor ceramic.

Description

Detailed Description of the Invention

[0001]

The present invention has a high dielectric constant, an excellent temperature characteristic of capacitance, and a high dielectric breakdown voltage (S
The present invention relates to an r, Ca) TiO ₃ -based semiconductor ceramic capacitor element body and a method for manufacturing the same.

[0002]

2. Description of the Related Art Japanese Unexamined Patent Publication No. 58-21312 (S)
r _1-x Ca _x ) Ti _y O _{2y + 1} , CeO ₂ , La
₂ O ₃ , WO ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Dy ₂ O ₃
Of at least one metal oxide of CuO, MnO
_A semiconductor ceramic capacitor element body comprising at least one metal oxide of ₂ , Bi ₂ O ₃ and PbO, and a method for manufacturing the same are disclosed. The porcelain composition has an apparent relative permittivity of 7,000 or more, a temperature characteristic of capacitance of a capacitor of ± 7% or less, a tan δ of 1.5% or less, and further insulation. Since the resistance R is 10 ⁴ MΩ (specific resistance ρ ^{10 10} Ω · cm) or more, it is possible to provide a semiconductor ceramic capacitor having relatively excellent characteristics.

[0003]

However, the semiconductor ceramic capacitor manufactured with the above composition has an effective dielectric constant of 800.
When it is 0 to 10000, the dielectric breakdown voltage (B · D · V) is about 1000 to 1200 V / mm. This is because the particle size of the element body is not uniform. Further, the semiconductor porcelain capacitor having the above composition is 13% in a reducing atmosphere.
The element body obtained by firing at 50 to 1450 ° C. for 3 hours (hereinafter referred to as “primary firing”) and the primary firing is heated in air for 9 hours.
Elements such as Cu, Mn, Bi, and Pb evaporate during baking at 00 to 1200 ° C. for 3 hours (hereinafter referred to as secondary baking), which causes compositional deviation. Therefore, a change in firing condition causes a change in electrical characteristics.

Therefore, an object of the present invention is to provide a semiconductor ceramic having a high dielectric breakdown voltage value and a method for manufacturing the same.

[0005]

The present invention for achieving the above object is achieved by using 99.200 to 99.915 mol% of (S
r _1-x Ca _x ) Ti _y O _{2y + 1} (where x = 0.31 to
0.52, y = 0.99 to 1.01) (hereinafter referred to as the first component) and 0.075 to 0.600 mol% of C.
At least one metal oxide selected from eO ₂ (cerium oxide), La ₂ O ₃ (lanthanum oxide), WO ₃ (tungsten oxide), Y ₂ O ₃ (yttrium oxide) and Nb ₂ O ₅ (niobium oxide). (Hereinafter referred to as the second component),
0.01 to 0.20 mol% of vanadium oxide (hereinafter,
(Referred to as a third component)). In addition, it is desirable to manufacture according to claim 2 or 3.

[0006]

FUNCTION AND EFFECT OF THE INVENTION Metal oxides (CuO, MnO ₂ , Bi ₂ O ₃ , P added conventionally for the purpose of insulating the grain boundaries).
bO) was segregated at the grain boundaries and combined with a part of the grain boundary components, or was present alone, and evaporated during firing. For this reason,
The diameter of the crystal particles became non-uniform, and the fluctuation of the characteristics became large due to the fluctuation of the firing conditions. On the other hand, when vanadium oxide (V ₂ O ₅ ) is used according to the present invention,
Vanadium (V) does not evaporate and compositional variation does not occur. Therefore, the crystal grain size becomes uniform, the dielectric breakdown voltage is improved, and when the effective dielectric constant is 8000 to 10000,
It becomes 4000 V / mm. The reason why vanadium (V) does not evaporate and the composition does not change is that V ₂ O ₅ becomes V ³⁺ by the primary firing in a reducing atmosphere and the perovskite type ABO ₃
B site of the main component {(Sr, Ca) TiO ₃ } having a crystal structure represented by (A: Sr, Ca, B: Ti), that is, T
It is considered that this is because the solid solution is completely formed on the i side.

[0007]

[First Embodiment] Next, a semiconductor ceramic capacitor according to an embodiment of the present invention (including a comparative example) and a method for manufacturing the same will be described. A mixture having the following composition was prepared so that the total amount was 100 mol%. First component (Sr _1-x Ca _x ) Ti _y O _{2y + 1} 99.61 mol% Second component CeO ₂ 0.33 mol% Third component V ₂ O ₅ 0.06 mol%

The first component is SrTiO ₃ (strontium titanate) and CaTiO ₃ (calcium titanate).
And are mixed in a ratio that satisfies (Sr _1-x Ca _x ) Ti _y O _{2y + 1} . SrTiO ₃ for obtaining the first component is SrCO ₃ (strontium carbonate) and T
iO ₂ (titanium oxide) was weighed equimolarly, stirred in a ball mill for 10 to 15 hours, dried and pulverized to 95
It was obtained by firing in the air at 0 to 1250 ° C. for 2 hours. For CaTiO ₃ , weigh CaCO ₃ (calcium carbonate) and TiO ₂ in equimolar amounts and use a ball mill to
After stirring for 0 to 15 hours, drying and crushing, 950-1
It was obtained by firing in air at 250 ° C. for 2 hours.

In order to investigate the characteristic change due to the change in the value of x in the first component, x is set to 0.
Eight samples from sample No. 1 to NO. 8 were made by changing from 28 to 0.56 in 8 steps. x is S of the first component
It is changed by changing the molar ratio of rTiO ₃ and CaTiO ₃ . For example, in sample No. 1, SrTi
72 mol% of O ₃ and 28 mol% of CaTiO ₃ are mixed to obtain the first component. As a result, x becomes 0.28. Also in sample Nos. 2 to 8, SrTi was changed depending on the value of x.
Determine the ratio of O ₃ and CaTiO ₃ . Sample No. 1-8
In the composition formula of the first component, y is 1
(Constant). Therefore, the composition formula of the first component of sample No. 1 is Sr _0.72 Ca _0.28 TiO ₃ .

Next, the first component, second component and third component of each sample
The mixture of components was stirred on a ball mill for 10 to 15 hours, dried, and then ground. Next, 10 to 15% by weight of polyvinyl alcohol was mixed as an organic binder and granulated, and this was granulated at a pressure of 1000 kg / cm ^{2 to} a diameter of 6.6.
After being formed into a circular disc having a thickness of 0.55 mm, a heat treatment is performed at 800 ° C. in order to remove the binder, and thereafter, it is baked at 1350 to 1450 ° C. for 3 hours in a reducing atmosphere (hereinafter referred to as primary baking). did. Next, the semiconductor porcelain body obtained by the primary firing is placed in air (in an oxidizing atmosphere) for 9 days.
Firing was performed at 00 to 1200 ° C. for 3 hours (hereinafter referred to as secondary firing) to obtain a porcelain body with insulated grain boundaries. Next in FIG.
As schematically shown in Fig. 2, silver paste was applied to both main surfaces of the porcelain body 1 and baked to form electrodes 2 and 3 to complete a capacitor. The porcelain body 1 is mainly composed of N-type semiconductor crystal grains 4 formed by primary firing and an insulating layer 5 formed mainly by secondary firing.

For comparison, a raw material mixture having the composition of the first component Sr _0.66 Ca _0.34 TiO ₃ 98.84 mol% the second component CeO ₂ 0.33 mol% and the third component CuO 0.83 mol% was prepared, Porcelain capacitors were produced in the same manner as in sample Nos. 1 to 8.

Next, the capacitance C and tan δ (dielectric loss) of the sample Nos. 1 to 8 and the capacitor of the comparative example were measured at a frequency of 1 kHz. Then, the apparent relative permittivity ε was obtained. In addition, the capacitance C _{20 of} 20 ° C., the capacitance C _-25 of −25 ° C., and the capacitance C ₈₅ of + 85 ° C. were measured to _obtain 20 ° C.
The rates of change T1 and T2 of the electrostatic capacitance at -25 ° C and + 85 ° C based on the above were determined by the following formula. _{T1 = {(C -25 -C 20} ) / C 20} × 100 (%) T2 = {(C 85 -C 20) / C 20} × 100 (%) Further, the specific resistance ρ of porcelain 1 It was determined by the formula of ρ = Rs / t. Where R is the insulation resistance value between the electrodes 2 and 3, and t is the element body 1.
Thickness, s is the electrode area, and in this embodiment, t is about 0.49 mm and s is about 19.635 mm ² . Moreover, the dielectric breakdown voltage BDV of the element body 1 was measured by applying a DC voltage. Table 1 shows the x value of the first component of sample No. 1 to 8,
ε, tan δ, ρ, BDV, T1 and T2 are shown. In the comparative example, ε is 10.000, tan δ is 0.9, and ρ is 8.0.
× 10 ¹⁰ Ω · cm, BDV was 1200 V / mm, T1 was 3.80%, and T2 was -2.90%.

[0013]

[Table 1]

In the present invention, ε is 7,000 or more, tan δ is 1.5% or less, ρ is 10 ¹⁰ Ω · cm or more, and BDV is 10%.
The standard for good products is 00 V / mm or more and the absolute value of T1 and T2 is 7% or less. Sample Nos. 2 to 7 according to the composition specified in the present invention satisfy the above-mentioned criteria for non-defective products. However, sample Nos. 1 and 8 are comparative examples because they are not included in the composition specified in the present invention and their characteristics do not satisfy the above criteria for non-defective products.

Comparative example (conventional example) in which the third component is CuO
According to the invention with BDV of 3 and V ₂ O ₅ as the third component
As is clear from comparison with BDV of Nos. 2 to 7, the BDV of the present invention can obtain BDV about 2 to 3 times that of the conventional example.

As shown in sample No. 1, when x of the first component is 0.28, T2 becomes larger than the reference value. Further, as shown in sample No. 1, when x of the first component is 0.56, ε and tan δ deviate from the reference. Therefore, the preferable range of x is 0.31 to 0.52.

When the mixing ratio of SrTiO ₃ and CaTiO _{3 as} the first component, that is, the value of x is changed, the temperature change rates T1 and T2 of the capacitance change. This is SrO-CaO-T
This is because the transformation point of the iO ₂ solid solution moves depending on the change in the compounding ratio of SrTiO ₃ and CaTiO ₃ , that is, the ratio of Sr and Ca. If the second component and the third component are fixed, ε, ρ, and BDV hardly change regardless of the change in x of the first component. In sample No. 8, when ε is 0.56, ε is 3,000 and tan δ is as bad as 1.9 because oxidation progresses to the crystal grains during the secondary firing.

Since the third component V ₂ O ₅ hardly evaporates in the primary and secondary firings, the composition of the porcelain body 1 after firing is substantially the same as the composition of the raw material before firing.

[0019]

Second Example First component (Sr _1-x Ca _x ) Ti _y O _{2y + 1} 99.61 mol% Second component CeO ₂ 0.33 mol% Third component V ₂ O ₅ 0.06 mol % Mixture was prepared as in the first example. However, the first
Four samples were prepared by keeping x of the component constant at 0.34 and changing y in four steps as shown in Table 2. The first
The mixing ratios of the raw materials shown in mol% of the components are as follows. Sample NO.SrTiO ₃ CaTiO ₃ SrCO ₃ TiO ₂ 9 66.68 34 1.32 0 10 65.34 34 0.66 0 11 66 34 0 0.5 12 12 66 34 0 1.0

A porcelain capacitor was manufactured by the same method as in Example 1 except that the composition of the raw materials was changed as described above, and the characteristics were measured. The results shown in Table 2 were obtained.

[0021]

[Table 2]

As is apparent from Table 2, y of sample No. 9
No. 1 was 0.98, no sintered body was obtained, and sample No. 1
When y of 2 is 1.02, ε and tan δ deteriorate. Therefore, the preferable range of y is 0.99 to 1.01.

[0023]

[Third Example] In order to investigate the preferable range of the third component V ₂ O ₅ , the first component (Sr _0.66 Ca _0.34 ) TiO ₃ 99.37 to 99.965 mol% the second component CeO ₂ 0.33 Mol% (constant) Third component V ₂ O ₅ A raw material of 0.005 to 0.300 mol% was prepared. The third component was changed in 9 steps as shown in Table 3. The first component is SrTiO ₃
It is a mixture of 66 mol% and CaTiO ₃ 34 mol%. A porcelain capacitor was manufactured by the same method as in Example 1 except that the composition was changed, and the characteristics were examined. The results shown in Table 3 were obtained.

[0024]

[Table 3]

As is clear from Table 3, BDV is poor when the third component of sample NO. 13 is 0.005 mol%, and ε when the third component of sample NO. 21 is 0.30. tan
δ, ρ, BDV are bad. Therefore, the preferable range of V ₂ O ₅ as the third component is 0.01 to 0.2 mol%.

[0026]

[Fourth Embodiment] In order to confirm that various metal oxides as the second component can be used in various proportions, the first component (Sr _0.66 Ca _0.34 ) TiO ₃ 99.865 to 99.34 mol% Second component CeO ₂ 0.075 to 0.600 mol% Third component V ₂ O ₅ 0.06 mol% (constant) 15 kinds of samples were prepared in the same manner as in the first embodiment. When a porcelain capacitor was produced and its characteristics were measured, the results shown in Table 4 below were obtained.

[0027]

[Table 4]

As is apparent from Table 4, CeO ₂ , Y ₂ O ₃ , La ₂ O ₃ , WO ₃ and Nb ₂ O ₅ were used as the second component.
It is possible to obtain a porcelain capacitor satisfying the standard of non-defective products by using any one of the above in the range of 0.075 to 0.600 mol% and setting the third component to V ₂ O ₅ . The second
The components are CeO ₂ , La ₂ O ₃ , WO ₃ , Y ₂ O ₃ and Nb.
It has been confirmed that the same effect as in one case can be obtained even if a plurality of kinds of metal oxides of ₂ O ₅ are combined.

The following has been confirmed by the above-mentioned embodiments and experiments. (A) The first component (Sr _1-x Ca _x ) Ti _y O _{2y + 1} shown in Examples 1 to 3 is SrTiO ₃ and Ca.
Similar results can be obtained by making from a composition composition other than TiO ₃ . For example, even if SrCO ₃ , CaCO ₃ , and TiO ₂ are synthesized, the same results as in the present embodiment can be obtained. (B) The heating temperature in the reducing atmosphere is preferably 13
The temperature is in the range of 0 to 1500 ° C., more preferably 135
It should be in the range of 0 to 1450 ° C. Further, this processing time is preferably 2 to 8 hours. (C) Reoxidation treatment (secondary firing) is 850 to 1300 ° C
It is preferable to carry out for 1 to 5 hours. (D) Other substances such as Al ₂ O ₃ and SiO ₂ may be added within a range that does not impair the properties of the capacitor body according to the present invention. (E) The present invention can also be applied to a case where a green sheet (unfired porcelain sheet) coated with an electrode material is laminated and fired to produce a laminated capacitor.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a ceramic capacitor of an example.

[Explanation of symbols]

 1 Porcelain body 2, 3 electrodes

Claims (3)

[Claims] 1. 99.200 to 99.915 mol% of (Sr _1-x Ca _x ) Ti _y O _{2y + 1} (where x = 0.31)
˜0.52, y = 0.99 to 1.01) and 0.075 to 0.600 mol% CeO ₂ (cerium oxide), La ₂ O ₃ (lanthanum oxide), WO ₃ (tungsten oxide). ), Y ₂ O ₃ (yttrium oxide) and Nb ₂
A semiconductor porcelain containing at least one metal oxide of O ₅ (niobium oxide) and 0.01 to 0.20 mol% of vanadium oxide. 2. 99.200 to 99.915 mol% of (Sr _1-x Ca _x ) Ti _y O _{2y + 1} (where x = 0.31)
˜0.52, y = 0.99 to 1.01) and 0.075 to 0.600 mol% CeO ₂ (cerium oxide), La ₂ O ₃ (lanthanum oxide), WO ₃ (tungsten oxide). ), Y ₂ O ₃ (yttrium oxide) and Nb ₂
Preparing a mixture of at least one metal oxide of O ₅ (niobium oxide) and 0.01 to 0.20 mol% of vanadium oxide, and molding the mixture into a predetermined shape A method of manufacturing a semiconductor porcelain, comprising: a step of obtaining a body; a step of firing the molded body in a non-oxidizing atmosphere to obtain a sintered body; and a step of heat-treating the sintered body in an oxidizing atmosphere. 3. The (Sr _1-x Ca _x ) Ti _y O _{2y + 1} is a mixture of CaTiO ₃ and SrTiO _3.
A method for manufacturing the semiconductor porcelain described.