JPH04282507A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a dielectric porcelain composition which has a high dielectric constant, a large quality coefficient Q and a region of-0 temperature coefficient tauf on a resonance frequency, and suitability for a microwave region. CONSTITUTION:A dielectric porcelain composition of titanium, barium, praseodymium, gadolinium system expressed by a composition formula of a.BaO.b TiO2.c{x.Pr2O11/3, (1-x).Gd2O3} (where a, b, c are mole ratio and a+b+c=1, 0.1<a<0.2, 0.6<b<0.8, 0.1>c>0.2, 0.1<x<0.8).

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dielectric ceramic composition suitable as a material for dielectric resonators and the like. The dielectric ceramic composition of the present invention is applicable not only to dielectric resonator materials but also, for example, to dielectric substrates for microwave ICs, dielectric adjustment rods, raw materials for composite materials with organic substances, and the like.

0002

2. Description of the Related Art Recently, electric resonators have come into widespread use in mobile radio equipment such as car telephones and cordless telephones that utilize radio waves in the microwave band from the MHz band to the GHz band. The dielectric ceramic composition used for such a dielectric resonator has a large relative dielectric constant εr, and
Characteristics such as a small temperature coefficient τf of the resonance frequency and a large quality factor Q (no-load Q0) are required.

Conventionally, such dielectric ceramic compositions include TiO2, MgO-CaO-TiO2, ZrO2-
Products whose main components are TiO2-SnO2, BaO-TiO2, etc. are known, but they have large temperature coefficients,
It is difficult to put it into practical use because the quality factor Q in the microwave band is small.

[0004] Also, a proposal regarding a BaO-TiO2-Nd2O3-based dielectric ceramic composition {Ber. Dt.
Keram. Ges. 55 (1978) No.
7; Japanese Unexamined Patent Publication No. 60-35406, etc.), but the quality factor Q is small and the relative permittivity εr is not sufficient.

[0004] Also, Ba(Mg1/3, Ta2/3)O
3 and Ba(Zn1/3, Ta2/3)O3 Ba(Z
Dielectric ceramic compositions having a perovskite structure such as those based on n1/3, Nb2/3)O3 have been proposed; .1 When used as a resonator in the 4 GHz band, there is a drawback that the resonator cannot be sufficiently miniaturized.

[0005] To solve this problem, Japanese Patent Application Laid-Open No. 62-72558 discloses BaO-TiO2-
A dielectric ceramic composition based on Nd2O3-BiO2/3 has been proposed. Its characteristics include a relative dielectric constant εr of 80 to 8
3. Quality factor Q is 1900-2650 and τf is 3
-10, which is a considerable improvement, but it is still insufficient, and there is a desire to develop a dielectric ceramic composition with even better properties.

[0006]

[Problem to be solved by the invention] As explained above,
Conventional dielectric ceramic compositions all have the characteristics that are required as dielectric resonator materials in recent years.
That is, the relative permittivity εr and the quality factor Q are higher, and τ
There is a problem that there is no material that has a small f. The present invention was made in view of these problems, and its purpose is to provide a dielectric ceramic composition that has higher relative dielectric constant εr, higher quality factor Q, and lower τf. .

[0007]

[Means for Solving the Problems] In order to solve the above problems, as a result of intensive study on the composition of dielectric ceramics, it was discovered that an excellent dielectric material could be obtained by using praseodymium and gadolinium, and the present invention was completed. reached. That is, the present invention has the compositional formula a.BaO.b.
TiO2・c {x・Pr2O11/3, (
1-x)・Gd2O3} (where a, b, c are molar ratios, a+b+c=1, 0.1<a<0.2
, 0.6<b<0.8, 0.1<c<0.2,
It is a titanium, barium, praseodymium, and gadolinium-based dielectric ceramic composition expressed by 0.1<x<0.8).

The present invention will be explained in more detail below. The present invention is characterized by the use of barium, titanium, praseodymium, and gadolinium, and their composition ratio, and is particularly characterized by praseodymium and gadolinium. That is, the total molar ratio of Pr2O11/3 and Gd2O3 c
is 0.1<c<0.2, and Pr2O11
x, which indicates the ratio of /3 and Gd2O3, is 0.1<
By having a composition represented by x<0.8, an excellent dielectric material suitable for the microwave band with a quality factor Q ~ 5050, a relative dielectric constant εr ~ 83, and a temperature coefficient τf of the resonance frequency ~ 0 can be obtained. It is.

The reason for limiting the composition range is as follows. a
When BaO is less than 0.1, the relative permittivity εr is small, and when it is more than 0.2, the quality factor Q is undesirable. Therefore, a is preferably in the range of 0.1<a<0.2, more preferably 0.12<a<0.
18 is good. When TiO2 is less than 0.6, the sinterability decreases, and when it is more than 0.8, the temperature coefficient of resonance frequency τ
f becomes large, which is not preferable. Therefore, b is
The range of 0.6<b<0.8 is preferable, and the range of 0.64<b<0.76 is more preferable. c is 0.1
If the dielectric constant εr is less than 0.2, the dielectric constant εr is small, and if it is 0.2 or more, the dielectric constant εr and the quality factor Q are both small, which is not preferable. Therefore, c is preferably in the range 0.1<b<0.2, more preferably 0.12<c<0.
．． 18 is good. x is 0.1 or less or 0.8
In the above case, the temperature coefficient τf of the resonance frequency becomes large, which is not preferable. Therefore, the range of x is preferably 0.1<x<0.8, more preferably 0.2<x<0.
．． 6 is good.

[0010] The dielectric ceramic composition according to the present invention may ultimately be an oxide ceramic composition, and as is usually done, barium (Ba), titanium (Ti), praseodymium (Pr), gadolinium (Gd) can be used. ) or other oxides,
It can be produced by mixing and firing starting materials that become oxides by thermal decomposition such as carbonates, basic carbonates, nitrates, hydroxides, and organic acid salts. After mixing and calcining the starting materials, the resulting calcined powder may be put to practical use in its original form by compounding it with an organic material or the like.

Next, a method of mixing and calcining starting materials, then shaping and sintering (a method used in applications such as resonators) will be explained. First, starting materials are mixed in predetermined amounts. When mixing, a method with high miscibility such as wet mixing with water, alcohol, other organic solvents, etc. is preferred. When wet mixing is performed, the resulting mixture is calcined after removing the solvent. Calcination is performed at a temperature of 900 to 130°C in an oxygen gas-containing atmosphere such as an air atmosphere.
It is preferable to carry out the reaction at about 0°C. Calcining temperature is 900
If the temperature is lower than ℃, the solid phase reaction due to calcination will not be promoted, and
If the calcination temperature exceeds 1300°C, the calcination powder will aggregate and the powder properties will deteriorate, which is not preferable.

[0012] The obtained calcined product is pulverized and then molded. As the molding method, general ceramic powder molding methods such as pressure molding, extrusion molding, sheet molding, injection molding, etc. are applied. At this time, additive components such as ordinary organic binders such as polyvinyl alcohol, plasticizers, and dispersants are added as necessary. The obtained molded body is sintered. Sintering is preferably performed at a temperature of about 1300 to 1500°C in an oxygen gas-containing atmosphere such as an air atmosphere.

The sintered body of the dielectric ceramic composition obtained in this way can be used as it is or by processing it into an appropriate shape and size as necessary to produce a dielectric resonator, a dielectric substrate for microwave IC, a dielectric It can be used as a material for body adjustment rods, etc., and has particularly excellent effects when used as a dielectric resonator used in the 0.1 to 4 GHz band.

[0014]

[Examples 1 to 20 and Comparative Examples 1 to 4] The present invention will be explained in detail below with further examples and comparative examples. High purity BaCO3, TiO2, Pr6O11, G as starting materials
After weighing the d2O3 powder to a predetermined composition ratio, wet mixing was performed using a ball mill for 20 hours. After heating and drying this slurry, it was placed in air at a temperature of 105
The calcined product was calcined at 0° C. for 2 hours, and the calcined product was wet-milled again for 20 hours using a ball mill. After the obtained slurry was heated and dried, an appropriate amount of polyvinyl alcohol was added, kneaded, and granulated through a 32-mesh sieve. The granulated powder was pressure molded at a molding pressure of 800 kg/cm 2 and fired in air at a temperature of 1350° C. to 1500° C. for 5 hours.

The obtained sintered body was processed into a cylindrical shape with a diameter of about 10 mm and a height of about 4 mm. The resonant frequency fo, quality factor Q, and dielectric constant εr of this sintered body were determined by measuring εr, quality factor Q, and τf in the GHz band by a transmission method using a cavity type resonator. For measurements, a Yokogawa Hewlett-Packard network analyzer (
The measurement was carried out using Murata Manufacturing Co., Ltd. (model number: DRG 8553) as a measuring jig. Furthermore, the TE01δ mode was used as the resonance mode. The resonant frequency of the sample was 3-4 GHz. In general, when measuring dielectric properties in the GHz band, the measured values often differ depending on the measuring method, and when comparing the measured values, it is necessary to give sufficient consideration to the measuring method. In particular, care must be taken when measuring the quality factor Q. Regarding the temperature dependence of the resonant frequency fo,
Measured in the range of -30 °C to +80 °C, temperature coefficient τ
I found f. The experimental results are shown in Table 1. In addition,
The value of the quality factor Q in Table 1 is calculated using the relational expression fo x Q = constant between the resonance frequency fo and the quality factor Q.
The values are shown converted to Hz.

[0016]

[Table 1]

[0017]

Effects of the Invention The dielectric ceramic composition of the present invention uses praseodymium and gadolinium as main components in addition to barium and titanium, so it has a high dielectric constant and a quality factor of Q.
is large, the stability of τf is good, and 0.1 to 4
It is particularly suitable as a dielectric material used in the GHz band and exhibits excellent effects.

Claims (1)

[Claims] [Claim 1] Compositional formula a・BaO・b・
TiO2・c{x・Pr2O11/3, (1
-x)・Gd2O3} (where a, b, c are molar ratios, a+b+c=1, 0.1<a<0.2,
0.6<b<0.8, 0.1<c<0.2, 0.
A titanium-, barium-, praseodymium-, and gadolinium-based dielectric ceramic composition represented by 1<x<0.8).