JP3385626B2 - Dielectric porcelain composition - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition, and more particularly, to a dielectric material having a high dielectric constant, excellent temperature characteristics, and low voltage dependency. The present invention relates to a dielectric ceramic composition having excellent characteristics as a dielectric material of a capacitor, which has a large insulation resistance even when used for a large product. 2. Description of the Related Art Barium titanate-based dielectric porcelain compositions widely used as dielectrics generally have a high dielectric constant, and have poor temperature characteristics. There are many excellent things. [0003] However, the barium titanate-based dielectric porcelain composition has a problem that the voltage dependence of its characteristics is large and the dielectric loss becomes extremely large when an AC high voltage is applied. Further, SrTiO ₃ —CaTiO ₃ —PbT
In iO ₃ -Bi ₂ O ₃ -TiO ₂ based dielectric ceramic composition, as high dielectric constant, is proposed having a small the voltage dependence, is also one which is put into practical use. However, in this dielectric ceramic composition, there is a problem that the temperature change rate of the capacitance is large, and, in order to improve the temperature characteristics, those in which a metal oxide such as CuO or NiO is added, For example, when used for a large product having a diameter of 20 mm or more and a thickness of 10 mm or more, the inside is easily converted to an n-type semiconductor, the insulation resistance is reduced, and a high-temperature load life test causes deterioration in a short time and breaks down. There is a problem. The present invention solves the above-mentioned problems, and has a high dielectric constant, excellent temperature characteristics, a small voltage dependency, and a large insulation resistance even when used in a large product. An object is to obtain a dielectric ceramic composition having a practically sufficient life. In order to achieve the above object, the dielectric ceramic composition of the present invention comprises SrTiO ₃ , CaTiO ₃ , PbTiO ₃ , Bi ₂ O ₃ ,
And TiO _2, SrTiO _3: 20~44 wt% CaTiO _3: 12 to 28 wt% PbTiO _3: 6 to 22 _{wt% Bi 2 O 3: 1 2} ~40 wt% TiO _2: proportion of 2 to 14 wt% The content of the rare earth element oxide such as CeO ₂ and Al ₂ O ₃ is 0.1 to 0.8% by weight with respect to the main component of the rare earth element oxide such as CeO _2. Al ₂ O ₃ : Dielectric ceramic composition added at a ratio of 0.1 to 1.0% by weight.
At -30 to 85 ° C. based on 20 ° C.
When the rate of change of the capacitance is within ± 5% (within the range of A characteristic)
Characterized in that that. Examples of the present invention will be described below together with comparative examples to clarify the features of the present invention. In this embodiment, in preparing a dielectric porcelain composition, first, the purity of S is higher than 98.0%.
rTiO ₃ , CaTiO ₃ , PbTiO ₃ , Bi ₂ O ₃ , T
iO ₂ , Al ₂ O ₃ and CeO ₂ are prepared, and these raw materials are
It is weighed so as to have a composition ratio as shown in Table 1. [Table 1] In Table 1, samples marked with an asterisk (sample numbers 15 to 24) indicate comparative examples having compositions outside the scope of the present invention, and other samples (sample numbers 1 to 14). ) Shows examples having compositions within the scope of the present invention. Next, the weighed raw materials are put into a polyethylene pot together with water and PSZ (partially stabilized zirconia) balls, and ground and mixed by a wet method. The mixture is then dewatered, dried, calcined at about 1000 ° C. for 2 hours and ground. Then, a polyvinyl alcohol (PVA) -based organic binder is added to the calcined powder in an amount of 1 to 2% by weight, put again in a polyethylene pot together with water and PSZ (partially stabilized zirconia) balls, and wet-milled. ,
After mixing, dehydration and drying, the particle size is adjusted through a 50 mesh sieve. [0013] Then, the obtained raw material powder is reduced to about 2 t /
After pressure molding into a disk having a diameter of 35 mm and a thickness of 20 mm under a pressure of cm ^2, the disk-shaped molded body is fired at 1150 to 1300 ° C. for 2 to 4 hours. Then, silver electrodes are applied and baked on both surfaces of the obtained sintered body, terminals are attached to the silver electrodes, and epoxy resin coating is performed to prepare a capacitor as a sample. With respect to the capacitor obtained as described above, the relative dielectric constant ε _{r at} 1 kHz and 1 vrms,
1 kHz, tan δ at 1 vrms, capacitance at −30 to 85 ° C. based on 20 ° C. (1 k
Hz, 1 vrms) temperature change rate TC (A characteristic) , 2
tanδ (A) when an AC voltage of kvrms / mm is applied.
C voltage characteristic), and the capacitance (1 kHz, 1 vrms) after performing a 3000-hour high-temperature load test at 100 ° C. and a DC voltage of 2.8 kv / mm. Table 2 shows the results. [Table 2] In Table 2, each sample number corresponds to the sample number in Table 1, and a sample number with an asterisk indicates a comparative example of a composition outside the scope of the present invention. An embodiment within the scope of the present invention will now be described. According to Tables 1 and 2, the dielectric ceramic composition of the comparative example has a relative dielectric constant of 690 as shown in sample No. 21, for example.
Even if it is large, it will be destroyed within 10 hours in a high-temperature load test, and its temperature characteristics, voltage dependence, and other characteristics such as difficulty in causing deterioration in a high-temperature load test On the other hand, the dielectric ceramic compositions of the examples have a relatively large relative dielectric constant of 500 or more, and have a temperature characteristic and a voltage dependency, and furthermore, a high temperature load. It can be seen that for each of the various characteristics such as the difficulty in causing deterioration in the test, characteristics that are not particularly problematic in practical use are obtained. Next, the reason why the composition range of each component is limited will be described. In limiting the range of each composition in the dielectric ceramic composition of the present invention, Tables 1 and 2 were used.
In addition to the data shown in Table 1, data other than Tables 1 and 2 are also considered. [SrTiO ₃ ] When the ratio of SrTiO _{3 in} the main component is less than 20% by weight, the temperature change rate TC of the capacitance on the low temperature side is JIS.
Out of the range of the A characteristic. If the ratio of SrTiO ₃ exceeds 44% by weight, the temperature change rate TC of the capacitance on the high temperature side is out of the range of the A characteristic and the relative dielectric constant ε
_r drops below 500 (sample no. 15). Therefore, the ratio of SrTiO _{3 in} the main component is preferably in the range of 20 to 44% by weight. [CaTiO ₃ ] When the proportion of CaTiO _{3 in} the main component is less than 12% by weight, the temperature change rate TC of the capacitance is out of the range of the A characteristic of JIS, and when the AC voltage of 2 kvrms / mm is applied.
The tan δ exceeds 3% (Sample No. 19). In addition, CaT
When the ratio of iO ₃ exceeds 28% by weight, the relative dielectric constant ε _r becomes 5
While decreasing to less than 00, the sinterability decreases (Sample No. 18). Therefore, the proportion of CaTiO _{3 in} the main component is preferably in the range of 12 to 28% by weight. [PbTiO ₃ ] When the proportion of PbTiO _{3 in} the main component is less than 6% by weight, the temperature change rate TC of the capacitance on the high temperature side becomes JIS.
Out of the range of the A characteristic, and the relative permittivity ε _r is 50
It falls below 0. When the proportion of PbTiO ₃ exceeds 22% by weight, the temperature change rate TC of the capacitance on the low temperature side falls outside the range of the A characteristic, and tan δ exceeds 1%. Furthermore, when an AC voltage of 2 kvrms / mm is applied, ta
nδ exceeds 3% (Sample No. 20). Therefore, the proportion of PbTiO _{3 in} the main component is preferably in the range of 6 to 22% by weight. [0022] If the ratio of the _{[Bi 2 O 3] Bi 2} O 3 in the main component is less than 1 2% by weight,
The temperature change rate TC of the capacitance is out of the range of the JIS A characteristic. Further, when the ratio of Bi ₂ O ₃ exceeds 40% by weight,
As the sinterability decreases, the AC voltage becomes 2 kvrms / mm
The tan δ at the time of application exceeds 3% (Sample No. 16). Accordingly, the ratio of Bi ₂ O ₃ in the main component is preferably in the range of 1 2 to 40 wt%. [TiO ₂ ] When the proportion of TiO _{2 in} the main component is less than 2% by weight, sintering stops (sample No. 17) and the proportion of TiO ₂ becomes 14%.
If it exceeds 10% by weight, it will break in the high temperature load test (that is, the effect of TiO ₂ addition will be lost) (Sample No. 2
1). Therefore, the proportion of TiO _{2 in} the main component is 2 to
It is preferably in the range of 14% by weight. The addition of the rare earth element oxide such as CeO ₂ [rare-earth element oxide such as CeO _2] (content)
However, if it is less than 0.1% by weight, the effect of addition is lost.
If the amount (content) of the rare earth element oxide such as CeO ₂ exceeds 0.8% by weight, the temperature change rate TC of the capacitance on the high temperature side falls outside the range of the A characteristic,
The relative dielectric constant ε _r decreases to less than 500 (Sample No. 2
3). Therefore, the proportion of the rare earth element oxide such as CeO ₂ is preferably in the range of 0.1 to 0.8% by weight. In the above embodiment, the case where CeO ₂ is used as the rare earth element oxide has been described.
In addition to O ₂ , Y (yttrium), La (lanthanum)
The same effect can be obtained when an oxide such as is used. [Al ₂ O ₃ ] If the added amount (content) of Al ₂ O ₃ is less than 0.1% by weight, it will break in a high-temperature load test (sample No. 22). If the addition amount (content) of Al ₂ O ₃ exceeds 1.0% by weight, the temperature change rate TC of the capacitance on the high temperature side is out of the range of the A characteristic, and the relative dielectric constant ε _r is 500. (Sample No. 24). Therefore,
The proportion of Al ₂ O ₃ added is preferably in the range of 0.1 to 1.0% by weight. The composition of the dielectric porcelain composition of the present invention is not limited to the above-mentioned embodiment, but may be modified by changing the ratio of each component within the scope of the present invention. It is possible. As described above, the dielectric porcelain composition according to the present invention comprises SrTiO ₃ : 20 to 44% by weight, CaTi
O _3: 12 to 28 wt%, PbTiO _3: 6~22 _{wt%, Bi 2 O 3: 1} 2 ~40 wt%, TiO _2: 2~14
Relative earth element oxide such as CeO ₂ : 0.1 to 0.8% by weight, Al ₂ O ₃ : 0.
Since 1 to 1.0% by weight is added, the relative dielectric constant is 50%.
A dielectric ceramic composition having a relatively large value of 0 or more, having excellent temperature characteristics and low voltage dependency, and having excellent characteristics as a dielectric material can be obtained. Further, the dielectric porcelain composition of the present invention comprises:
Even when used for a large product, it is possible to obtain a highly reliable capacitor which is hard to be an n-type semiconductor inside, has a large insulation resistance, and does not deteriorate even in a high temperature load test. Therefore, the dielectric ceramic composition of the present invention is particularly significant as a dielectric material for a high-voltage capacitor.

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Claims (1)

(57) [Claims 1] SrTiO ₃ , CaTiO ₃ , PbTiO
_3, Bi ₂ O _3, and TiO _2, SrTiO _3: 20~44 wt% CaTiO _3: 12 to 28 wt% PbTiO _3: 6 to 22 _{wt% Bi 2 O 3: 1 2} ~40 wt% TiO _2: Rare earth element oxides such as CeO ₂ and Al ₂ O ₃ , relative to the main component contained at a ratio of 2 to 14% by weight, are rare earth oxides such as CeO ₂ : 0. 1 to 0.8 wt% Al ₂ O _3: a dielectric ceramic composition was added in an amount such that 0.1 to 1.0 wt%
At -30 to 85 ° C. based on 20 ° C.
When the rate of change of the capacitance is within ± 5% (within the range of A characteristic)
The dielectric ceramic composition characterized by that.