JPS6364888B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a composition for a reduction and reoxidation type semiconductor ceramic capacitor. Conventionally, reduction and reoxidation type semiconductor ceramic capacitors are
Rare earth elements or Nb, Ta, etc. are added to BaTiO ₃ -based porcelain, and it is made into a semiconductor through reduction heat treatment in an oxidizing, neutral, or reducing atmosphere, and then re-oxidized to make the surface of the semiconductor porcelain an insulator. One in which a silver electrode is formed is in practical use.
However, this type of capacitor has the disadvantage that increasing the capacitance reduces the breakdown voltage and increases dielectric loss, and conversely, increasing the breakdown voltage decreases the capacitance. In order to improve this drawback, the special public
In Publication No. 40965, BaTiO ₃ is used as a substrate, and this
Bi ₂ O ₃ 1-4% by weight, ZrO ₂ 1.6-5% by weight, Mn0.01
~0.10% by weight, and between the amount of ZrO ₂ added (y) and the amount of Bi ₂ O ₃ added (x), x-1
There is a relationship of (weight%)≦y≦x+3 (weight%),
A reduced and reoxidized semiconductor ceramic composition is used, which is characterized in that there is a relationship of Z/X≦20% in terms of weight ratio between the amount of Mn added (z) and the amount of Bi ₂ O ₃ added (x). It was proposed to do so. Although reduction-reoxidation type semiconductor ceramic capacitors using this composition exhibit excellent characteristics such as small size, large capacity, low dielectric loss, and high breakdown voltage, they have large variations in breakdown voltage and are difficult to use at high frequencies (around 1MHz). Due to the large dielectric loss of the material, there was a problem that its applications were limited. The present invention has been made in view of these problems, and it is an object of the present invention to obtain a small, large-capacity reduction-reoxidation type semiconductor ceramic capacitor with high breakdown voltage, little variation, and low dielectric loss at high frequencies. The purpose of this invention is to provide a composition that allows for That is, the present invention provides (Ba _1-l Y _l )Ti _n O ₃ (however,
l and m are the mole fractions of each component, 0.002≦l≦
0.006, 1.02≦m≦1.08) 85 to 95 mol%, and (Ba _1-o
Sr _o ) ZrO ₃ (however, 0.1≦n≦0.3) 5 to 15 mol% as a base, Bi ₂ O ₃ 1 to 4% by weight, Mn 0.03 to
The gist thereof is a composition for a reduced and reoxidized semiconductor ceramic capacitor containing 0.1% by weight. In the present invention, the composition range is limited as described above for the following reason. In other words, if the mole fraction l of Y is less than 0.002, the dielectric loss in the high frequency range will increase, and if it exceeds 0.006, the variation in breakdown voltage will increase, and the minimum breakdown voltage (BDV _nio ) in the same lot will decrease. l
was set in the range of 0.002 to 0.006. The mole fraction (m) of Ti is set to 1.03 to 1.08 because if m is outside this range, the capacitance and/or breakdown voltage will decrease. The mole fraction (n) of S _r in (Ba _1-o Sr _o )Z _r O ₃ was set to 0.1 to 0.3 because if n is less than 0.1, the BDV _nio will not improve sufficiently, and if it exceeds 0.3, it will become static. This is because the capacitance decreases. Furthermore, the reason why the amount of Bi ₂ O ₃ added was set at 1 to 4% by weight is because if Bi ₂ O ₃ is less than 1% by weight, porcelain is difficult to be reduced, and the entire porcelain is easily reoxidized at the reoxidation temperature. This is because the capacitance becomes small, and if it exceeds 4% by weight, the capacitance becomes small. moreover,
The reason why the amount of Mn added was set to 0.03 to 0.1% by weight was because Mn
If it is less than 0.03% by weight, both the capacitance and insulation resistance will be small, and the breakdown voltage will also be small, and if it exceeds 0.1% by weight, the capacitance will be small. Hereinafter, the present invention will be explained according to examples. Example 1 BaCO ₃ , Y ₂ O ₃ and TiO ₂ were used as raw materials, and these were weighed and mixed to have a composition ratio of (Ba _0.998 Y _0.002 )Ti _1.03 O ₃ , while BaCO ₃ , SrCO ₃ and
ZrO ₂ is weighed and mixed to have a composition ratio of (Ba _0.90 Sr _0.10 )ZrO ₃ , and both mixtures are calcined at 1150°C. The generated (Ba _0.998 Y _0.002 ) Ti _1.03 O ₃ ,
(Ba _0.90 Sr _0.10 ) ZrO ₃ , Bi ₂ O ₃ and MnO ₂ as the first
Mix in the ratio shown in the table, crush with a binder, size the particles, use a press under pressure of 1000 kg/cm ² , diameter 10
mm, and form into a disc with a thickness of 0.5 mm. this in the air
After firing at 1320°C, reduction treatment is performed at 1200°C for 2 hours in a reducing atmosphere consisting of 15% hydrogen and 85% nitrogen by volume to convert it into a semiconductor, and the product is cooled in the reducing atmosphere. Next, the semiconductor ceramic element thus obtained was heated for 30 minutes at 1050°C for reoxidation treatment, and silver paste was applied to both surfaces of the thus obtained semiconductor ceramic element, dried, and then heated in air for 30 minutes.
Baking treatment was performed at 800° C. for 5 minutes to obtain a capacitor made of reduced and reoxidized semiconductor porcelain with a semiconductor inside and an insulating layer formed by reoxidation on the surface. The capacitance, breakdown voltage (BDV), and dielectric loss tangent (tan δ) at 1 MHz were measured for each reduction and reoxidation type semiconductor ceramic capacitor thus obtained. The results are shown in Table 1 along with the composition. Note that BDV ( ) is the average value of breakdown voltage for 100 samples, and BDV ( _nio ) is the lowest breakdown voltage among them. Example 2 Same as Example 1 (Ba _0.996 Y _0.04 ) Ti _1.05
O ₃ , (Ba _0.80 Sr _0.20 ) ZrO ₃ are generated, and these are
It was mixed with Bi ₂ O ₃ and Mn (in terms of MnO ₂ ) in the proportions shown in Table 2 to obtain a reduced and reoxidized semiconductor ceramic capacitor in the same manner as in Example 1. Their capacitance, breakdown voltage, and dielectric loss tangent are also shown in Table 2. Comparative Example 1 BaCO ₃ and TiO ₂ were weighed and mixed and calcined at 1150°C for 2 hours to produce BaTiO _3. On the other hand, BaCO ₃ and ZrO ₂ were weighed and mixed and calcined at 1150°C for 2 hours to produce BaZrO. ₃
Make a mixture of 90 mol% _BaTiO3 , 10 mol% _{BaZrO3 , 3} % by weight _Bi2O3 , 10% by weight _TiO2 ,
Binder (vinyl resin) after adding 0.05% Mn by weight
Add 3.5% by weight and size the particles to a diameter of 10mm and a thickness of 0.5mm.
It was formed into a disc. This disk was fired, reduced and reoxidized under the same conditions as in Example 1, then coated with silver paste and baked at 800°C to form an electrode.

【table】

[Table] A capacitor was obtained. Its capacitance is 150nF/
^cm2 , BDV(), 1.1KV, BDV( _nio )
0.4KV, tan δ (1MHz) was 18%. Comparative Example 2 (Ba _0.998 Y _0.002 ) Ti _1.03 prepared in Example 1
To a mixture of 90 mol% O ₃ and 10 mol% BaZrO ₃ prepared in Comparative Example 1, 2% by weight Bi ₂ O ₃ and 0.05% by weight Mn (calculated as MnO ₂ ) were added, and the mixture was prepared in the same manner as in Example 1. A reduced and reoxidized semiconductor ceramic capacitor was obtained. Its capacitance is 170nF/cm ² , BDV() is 1.2KV,
BDV (min) was 0.5KV and tanδ (1MHz) was 12%. Comparative example 3 BaTi _1.05 O ₃ 90 mol% and (Ba _0.80 Sr _0.20 ) ZrO ₃ 10
2% by weight of Bi ₂ O ₃ and 0.05% by weight of Mn were added to the mol% mixture, and a reduced and reoxidized semiconductor ceramic capacitor was obtained in the same manner as in Example 1. Its capacitance is
150nF/ ^cm2 , BDV() is 1.2KV, BDV(min)
was 0.6KV, and tanδ (1MHz) was 19%. As is clear from the results in Tables 1 and 2, the capacitor made of the reduced and reoxidized semiconductor ceramic composition according to the present invention has the same areal capacitance as the conventional capacitor of Comparative Example 1. Also, the minimum breakdown voltage is high, there is little variation in breakdown voltage, and the dielectric loss tangent at high frequencies is low, showing good characteristics. In addition,
From the results of Comparative Examples 1 to 3, it can be seen that when a part of Ba is replaced with Y, the dielectric loss is improved, and when a part of Ba is replaced with Sr, only the BDV (min) is slightly improved.

Claims (1)

[Claims] 1 (Ba _1-l Y _l )Ti _n O ₃ (However, 0.002≦l≦0.006,
1.02≦m≦1.08) 85 to 95 mol% and (Ba _1-o Sr _o )
Reduced and reoxidized semiconductor ceramic made by using 5 to 15 mol% of ZrO ₃ (0.1≦n≦0.3) as a base and adding 1 to 4% by weight of Bi ₂ O ₃ and 0.03 to 0.1% by weight of Mn. Composition for capacitors.