JPH04104946A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To improve specific dielectric constant, Q-value and temperature coefficient of resonant frequency of dielectric porcelain by reducing the usage of Sm2O3 by specifying composing ratio of a composition comprising BaO, TiO2, Nd2O3, Sm2O3 and Bi2O3. CONSTITUTION:In a composition expressed by xBaO-yTiO2-z[(1-a-b)Nd2O3-aSm2 O3-bBi2O3], each component is weighed so as to have a molar ratio satisfying 0.10<=x<=0.20, 0.60<=y<=0.75, 0.10<=z<=0.24, x+y+z=1, 0<a<=0.25 and 0<b<=0.30 and pure water is added, then resultant system is wet-mixed, thus fired at about 1000 deg.C, further about 1wt.% binder (e.g. PVA) is added and wet-crushed. Next, resultant system is dried, sieved and granulated, then molded, thus burned to afford the aimed dielectric porcelain.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a dielectric ceramic composition, particularly a high frequency dielectric ceramic composition suitable for dielectric resonators and the like.

(Background Art) With the development of high-frequency devices such as mobile phones in recent years, the dielectric resonators used in these devices are also required to be small and have high performance. The dielectric ceramic used in such a dielectric resonator is required to have the following characteristics. That is, first,
(1) High relative dielectric constant (εr). This is because if the dielectric constant is high, the resonator can be made smaller when used at a fixed frequency. Also, (2) Q
High value. When ceramic has a high Q value, a resonator using it can have low loss.

Furthermore, (3) when used as a resonator, the temperature coefficient (τf) of the resonant frequency is small. This is to minimize variations in characteristics due to temperature changes.

By the way, as a dielectric ceramic composition of this kind, Patent Publication No. 58-20905 discloses Bad-Ti.
○It has been revealed that 2 series or a part of it has been replaced with other elements, but such dielectric ceramics had a low dielectric constant of about 30 to 40 and a small Q. . Also, B shown in Japanese Patent Publication No. 59-23048
In compositions having a composite perovskite structure such as a(Mg+zsT a tiz>03), although Q is large, there is a problem that the dielectric constant is small at 30 to 40.

Moreover, in Japanese Patent Application Laid-open No. 102003/1983, Ba0-
A ceramic composition based on TiOx -NdzOs -B 1203 has been revealed, but although it has a very high relative dielectric constant, the temperature coefficient of the resonance frequency is large, so it is difficult to say that it has sufficient characteristics. , and furthermore, JP-A-57-
B a OT i O2N proposed in Publication No. 21010
The ceramic composition of the d zos mzo = system has the problem that the temperature coefficient of the resonance frequency is small and that it is not possible to obtain characteristics of a large dielectric constant. B a O-T i O,-NdzOs -3m disclosed in Publication No. 100906
When using a zO3BizO3-based ceramic composition in a resonator, its dielectric constant is still not large enough to be sufficiently miniaturized, and moreover, it requires 7 to 20 mo1% of samarium oxide, an expensive raw material. Since it is necessary to contain it, there is also a problem in terms of cost.

(Solution section B) The present invention was made against this background, and its object is to have a high dielectric constant, a large Q, and a temperature at the resonant frequency. An object of the present invention is to provide a dielectric ceramic composition whose coefficient can be reduced at low cost.

(Solution Means) In other words, in order to solve the problem, the present invention was completed based on the facts found as a result of various studies on the composition of many dielectric ceramics, and the gist thereof is as follows. , composition formula: % formula %) A dielectric ceramic composition consisting of barium oxide, titanium oxide, neodymium oxide, samarium oxide, and bismuth oxide, in which χ, y, z, a, and b are , respectively, is a dielectric ceramic composition characterized in that it is configured to satisfy the following formula: % formula %.

Thus, the dielectric ceramic composition according to the present invention contains barium oxide (Bad), titanium oxide (Tilt), neodymium oxide (NdzOs), and samarium oxide (SmzOs).
), and bismuth oxide (Bit03), and each of these components is contained in a specific amount, as can be expressed by the above compositional formula, and has excellent dielectric properties. It exhibits body porcelain characteristics and is Sm.

Since the amount of ○ used can be made extremely small compared to conventional dielectric porcelain, it has become possible to obtain a dielectric porcelain composition at an advantageous cost.

(Specific structure) By the way, in such a dielectric ceramic composition, when the content of BaO, which is one of the main components, is less than 10 mo1% (χ<0.10), the dielectric constant of the obtained dielectric ceramic composition decreases. There is a problem that the ratio becomes low, while 20mo1
% (χ>0.20), a problem arises in that the temperature coefficient of the resonance frequency becomes too large. In addition, regarding T i Oz, its content is 5
When Qmo is less than 1% (y<0.60), the Q value becomes large and deteriorates, while when it exceeds 75+++o1% (y>0.75), the temperature coefficient of the resonant frequency becomes too large. This causes the problem of storage.

In addition, regarding the total amount of NdzO3, S m t O3, and Bi, O, in other words, ((1-a-b)N d
tox a S mhos b B 1zch
), the total content is 10mo1%
When it is less than (z<0.10), the temperature coefficient of the resonance frequency becomes large, while when it exceeds 24w+o1% (z>0.24), the problem arises that sinterability deteriorates.

In addition, in the present invention, SmzO8 is used together with NdzOs.
and 13 iz Os (D use 4!, NdzOs
<7) Although an attempt was made to partially substitute S m z O3 and Bi2O2, in Notealka and Sono, N d ff
By replacing i O3 with S m t Os, the Q value can be improved and the temperature coefficient can be reduced.

In particular, to obtain the full effect of samarium replacement, 3II
It is desirable to replace 1% or more of IO (a≧0.03”), but if the samarium replacement amount is 25mol1%
(a > 0.25), a problem occurs in which the dielectric constant decreases, and samarium oxide has a high raw material unit cost, so from a cost perspective, it is practical to replace up to 1% of 251IIO. It becomes a limit.

Furthermore, when BizO* is substituted for NdzOs, the dielectric constant increases and the temperature coefficient of the resonance frequency can be reduced. In particular, in order to obtain a sufficient substitution effect with Bi2O2, it is desirable to substitute 5 mo1% or more (b≧0.05). However, when the amount of BtzOz substitution exceeds 30+no1% (b>0.3
0), the Q value becomes too low and cannot be put to practical use.

(Examples) Examples of the present invention are shown below to clarify the present invention more specifically, but the present invention is not limited in any way by the description of such examples. That goes without saying.

Furthermore, in addition to the embodiments shown below, various changes, modifications, improvements, etc. can be made to the present invention based on the knowledge of those skilled in the art, without departing from the spirit of the present invention. should be understood.

First, using high-purity barium carbonate, titanium oxide, neodymium oxide, samarium oxide, and bismuth oxide, these components were expressed in various moles shown as χ, y, z, a, and b in Tables 1 and 2 below. Weigh it so that it is the ratio,
The mixture was put into a polyethylene pot together with alumina cobbles, pure water was added, and wet mixing was performed. The resulting mixture was then removed from the pot and dried at 1000°C.
Calcining was performed in an air atmosphere for 2 hours. Next, the calcined product was again put into a polyethylene pot together with alumina boulders, and pure water was added thereto for wet pulverization.

At this time, 1% by weight of PVA was added as a binder so that the binder was uniformly mixed with the calcined powder. Thereafter, the obtained pulverized product was dried and granulated by passing it through a 40-mesh sieve.

Using the powder prepared in this way, it was molded using a press molding machine at a surface pressure of 1 ton/aa" of 20 mφ
A disk-shaped sample with a size of 5 m+t was molded. Next, each sample molded in this way was fired in air at a temperature of 1300 to 1400°C for 2 hours. Furthermore, each sample obtained by firing was polished to a size of 14+maφ×7mm.

The relative permittivity and unloaded Q of the various samples obtained in this way were measured by the known parallel conductor plate type dielectric resonator method, and the temperature coefficient (τ,) of the resonance frequency was determined by -25 Measurements were carried out in the range of °C to 75 °C, and the results are shown in Tables 1 and 2 below. Note that the measurement frequency was 3 to 4 GHz. Further, in Tables 1 and 2, Q is a value converted to a value at 3 GHz.

As is clear from the results in Tables 1 and 2, the dielectric ceramic compositions Nos. 1 to 23 and Nos. 28 to 42 according to the present invention all have a large dielectric constant and a high Q. temperature coefficient of resonance frequency (τf)
It was a small one. In contrast, the comparative example N
o, 24-27 and 43-48, at least the dielectric constant, Q value and temperature coefficient (τ
, ) - Table 11 (Effects of the Invention) As is clear from the above explanation, the present invention has a high relative dielectric constant, a large Q, and a low temperature at the resonant frequency. A dielectric ceramic composition with a small coefficient can be obtained, and such a dielectric ceramic composition can be manufactured at low cost because the amount of samarium oxide used is small.

Claims (1)

[Claims] Compositional formula: χBaO-yTiO_2-z [(1-a-b
)Nd_2O_3-aSm_2O_3-bBi_2O_
A dielectric ceramic composition consisting of barium oxide, titanium oxide, neodymium oxide, samarium oxide, and bismuth oxide, represented by The following formula: 0.10≦χ≦0.20 0.60≦y≦0.75 0.10≦z≦0.24 χ+y+z=1 0<a≦0.25 0<b≦0.30 A dielectric ceramic composition characterized in that it is configured as follows.