JPH04104949A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To obtain a dielectric porcelain composition having high specific dielectric constant, large Q and small temperature coefficient of resonant fre quency by making a specific composition comprising BaO, TiO2, Nd2O3, praseo dymium oxide and Bi2O3 as principal components. CONSTITUTION:The aimed dielectric porcelain composition is composed of barium oxide, titanium oxide, neodymium oxide, praseodymium oxide and bis muth oxide expressed by the composition formula. In the composition formula, x, y, z, a and b are respectively contained so a to satisfy 0.10<=x<=0.20; 0.60<=y<=0.75; 0.10<=z<=0.25; x+y+z=1; 0<a<=0.25 and 0<b<=0.30. In said porce lain composition, temperature coefficient of resonant frequency can be lowered by raising specific dielectric constant by substituting neodymium oxide with bismuth oxide and further, specific dielectric constant can be furthermore raised without reducing Q-value by substituting neodymium oxide with praseodymium oxide.

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 (τ,) 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, Japanese Patent Publication No. 5B-20905 discloses Ba0-Ti.
It has been revealed that the O□ system or a part of it is replaced with other elements, but such dielectric ceramics have 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 with a composite perovskite structure such as a (M g I/3T a !/3 ) 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. 56-102003, B a
O-T i O, -NdzOs -B izo+ type ceramic composition has been revealed, but although this has a very high dielectric constant, the temperature coefficient of the resonance frequency is large, so it is difficult to say that it has sufficient characteristics. Furthermore, the Ba0-TiO,-N proposed in JP-A No. 57-21010
In the case of dzOi-3mzO+ ceramic compositions, the temperature coefficient of the resonance frequency is large and there is an inherent problem in practical use.Furthermore, the BaO- Ti1t-Nd203P
The rb○ type ceramic composition had a large temperature coefficient of resonance frequency and was not practical.

(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. The object of the present invention is to provide a dielectric ceramic composition whose coefficient can be reduced.

(Solution Means) That is, in order to solve this 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. However, it is a dielectric ceramic composition consisting of barium oxide, titanium oxide, neodymium oxide, praseodymium oxide, and bismuth oxide, with the composition formula: % formula %), and χ, y, z, and a in the composition formula.
The dielectric ceramic composition is characterized in that b is configured to satisfy the following formula: % formula %.

Thus, the dielectric ceramic composition according to the present invention contains barium oxide (Bad), titanium oxide (TiO□), neodymium oxide (N d !03 ), praseodymium oxide (P
r zo++zs), and bismuth oxide (BizOx
) is the main component, and each of these components is
As can be expressed by the above compositional formula, each component is contained in a specific amount, thereby exhibiting excellent dielectric ceramic properties.

(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), the temperature coefficient of the resonant frequency becomes too thick (too much).
When it becomes less than 0mo1% (y<0.60), the Q value becomes large and deteriorates, while when it exceeds 75mo1% (y>0.75), the temperature coefficient of the resonance frequency becomes too large. This causes the problem of storage.

In addition, regarding the total amount of Nd, O, Pr11011/l, and Bi, O, in other words, ((1-a-b)Nd
2O2a P rzoIlyx bB 1zos )
Regarding the value of ), which causes the problem of poor sinterability.

In addition, in the present invention, in addition to Nd2O2, Pr, 0.
,．． 3 and the use of BizOx makes a part of Ndt03 P
It is intended to be replaced with rzOxy3 and BizCh, among which N d z O: + is replaced with Pr20
By replacing it with I+73, the dielectric constant can be increased. In particular, the amount of praseodymium substitution is 3 +
It is desirable to carry out substitution of 1% or more (a≧0.03). However, the amount of praseodymium replacement is 25mo1%
If it exceeds (a>0.25), the temperature coefficient becomes large, and therefore substitution up to 25 mo1% becomes the practical limit.

Furthermore, when Nd2O is replaced with BizOi, 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 81zOz, it is desirable to substitute 5 mo1% or more (b≧0.05). However, when the amount of Bitch substitution exceeds 3Qmo1% (b>0.30
), 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, high-purity barium carbonate, titanium oxide, neodymium oxide, praseodymium oxide, and bismuth oxide were used, and their components were determined by χ in Table 1 below.

They were weighed so as to have various molar ratios shown as y, z, a, and b, and put into a polyethylene pot together with alumina cobbles, pure water was added, and wet-mixed. The resulting mixture was then removed from the pot and dried.
Calcining was performed at 1000°C for 2 hours in an air atmosphere. Next, the calcined product was again mixed with alumina boulders.
The mixture was placed in a polyethylene pot, pure water was added, and wet pulverization was performed. At this time, 1% by weight of PVA was added as a binder.
In addition, the binder was mixed uniformly 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, a press molding machine was used to mold the powder to 20 mmφ at a surface pressure of 1 ton/CIm.
A disk-shaped sample with a size of ×15IIXIIlt was molded. Next, each sample molded in this way was heated in air at a temperature of 1300 to 1400°C.
It was baked for 2 hours. Furthermore, each sample obtained by this firing was polished to a size of 14 mmφ x 7 squares.

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

As is clear from the results in Table 1, the dielectric ceramic compositions Nos. 1 to 16 according to the present invention all have a large relative dielectric constant and a large Q value, as well as a low temperature coefficient of resonance frequency. (τ,) was small. On the other hand, in the dielectric ceramic compositions with Nα of 17 to 24, which are comparative examples, at least the dielectric constant, Q value, and temperature coefficient (
τf), the performance deteriorates,
In addition, samples Nos. 25 and 26 were not sintered.

(Effects of the Invention) As is clear from the above explanation, in the present invention, by replacing neodymium oxide with bismuth oxide, it is possible to increase the relative dielectric constant and lower the temperature coefficient, and By replacing neodymium oxide with praseodymium oxide in the above, Q4! ! The dielectric constant can be further increased without lowering the dielectric constant.

Claims (1)

[Claims] Compositional formula: χBaO-yTiO_2-z [(1-a-b
)Nd_2O_3-aPr_2O_1_1_/_3-b
Bi_2O_3] is a dielectric ceramic composition consisting of barium oxide, titanium oxide, neodymium oxide, praseodymium oxide, and bismuth oxide, and χ, y, z and a, b in the composition formula are, respectively, Below formula: 0.10≦
χ≦0.20 0.60≦y≦0.75 0.10≦z≦0.25 χ+y+z=1 0<a≦0.25 0<b≦0.30 dielectric ceramic composition.