JPH04329210A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a dielectric porcelain composition wherein the dielectric constant is high and the quality coefficient Q is great and which is suitable for a microwave region where the resonance frequency has a temperature coefficient tau f of a specified value. CONSTITUTION:There is provide a dielectric porcelain composition of barium, lead, titanium, lanthanum, praseodymium gadolinium system, expressed by the composition formula: a.[(1-w) BaO, w.PbO].b.TiO2.c.[x.La203.y.Pr2 O11/3.z.Gd2O3] (where a, b, c, x, y, and z represent molar rations, a+b+c=1, 0.1<a<0.2, 0.6<b<0.8, 0.1<c<0.2, 0.001<w<0.25, x+y+z=1, 0.01<x<0.85, 0.01<y<0.85, 0.1<z<0.75).

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, dielectric 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 in such a dielectric resonator has a large relative permittivity εr, a small temperature coefficient τf of the resonance frequency, and a quality factor Q(
Characteristics such as a large no-load Q0) are required.

Conventionally, such dielectric ceramic compositions include TiO2, MgO-CaO-TiO2, ZrO2-Ti
Products whose main components are O2-SnO2, BaO-TiO2, etc. are known, but they have a large temperature coefficient and a small quality factor Q in the microwave band, making it difficult to put them into practical use. be.

[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.

[0005] Also, Ba (Mg1/3, Ta2/3)
Dielectric ceramic compositions having a perovskite structure such as those based on O3, Ba(Zn1/3, Ta2/3)O3, or Ba(Zn1/3, Nb2/3)O3 have been proposed, but their dielectric constants are small. (Relative dielectric constant εr = 25~40
Therefore, when a resonator is used in the 0.1 to 4 GHz band, for example, it is difficult to make the resonator sufficiently compact.

To solve this problem, Japanese Patent Laid-Open No. 62-72558 discloses BaO-TiO2-N.
A dielectric ceramic composition based on d2O3-BiO2/3 has been proposed. Its characteristics include a relative dielectric constant εr of 80 to 83.
, the quality factor Q is 1900 to 2650, and τf is 3 to
10, which is a considerable improvement, but is still insufficient, and there is a desire to develop a dielectric ceramic composition with even better properties.

[0007]

[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. .

[0008]

[Means for Solving the Problems] In order to solve the above problems, as a result of intensive study on the composition of dielectric ceramics, we have found that a part of the barium is replaced with lead, and furthermore, lanthanum, praseodymium, and gadolinium are used to achieve excellent dielectric properties. The present invention was completed based on the discovery that the present invention can be obtained. That is, the present invention has the compositional formula a.{(1-w).Ba
O,w・PbO}・b・TiO2・c・{x
・La2O3 ・y ・Pr2O11/3・z ・G
d2O3 } (where a, b, c, x, y, z are molar ratios, a+b+c=1, 0.1<a<0.2, 0.6<
b<0.8, 0.1<c<0.2, 0.001<w<0
．． 25, x+y+z=1, 0.01<x<0.85
, 0.01<y<0.85, 0.1<z<0.7
5) is a barium, lead, titanium, lanthanum, praseodymium, and gadolinium-based dielectric ceramic composition.

The present invention will be explained in more detail below. The present invention is characterized by the use of barium, lead, titanium, lanthanum, praseodymium, and gadolinium and their composition ratios, and is particularly characterized by the ratios of barium to lead, lanthanum to praseodymium, and gadolinium. That is, the total molar ratio a of BaO and PbO is 0.1<a<0
．． 2, and w indicating the ratio of BaO 2 and PbO 2 is 0.
001<w<0.25, and also La2O3 and Pr2
The total molar ratio c of O11/3 and Gd2O3 is 0.1<
c<0.2, and x indicating the ratio of La2O3 is 0
．． 01<x<0.85, y indicating the ratio of Pr2O11/3 is 0.01<y<0.85, and Gd2O3
The quality factor Q ~ 6210 and the relative dielectric constant ε
An excellent dielectric material suitable for the microwave band with r ˜93 and temperature coefficient τf of the resonant frequency of ˜0 can be obtained.

The reason for limiting the composition range is as follows. a
When BaO is less than 0.1, the dielectric constant εr is small, and when it is more than 0.2, the quality factor Q is undesirably low. Therefore, a is preferably in the range of 0.1<a<0.2, more preferably 0.12<a<0.18.
Good. If TiO2 is less than 0.6, the sinterability will deteriorate, and if it is more than 0.8, the temperature coefficient τf of the resonance frequency will become large, which is not preferable. Therefore, b is 0.6
The range <b<0.8 is suitable, and more preferably
It is preferable that 0.64<b<0.76. When c is less than 0.1, the relative permittivity εr is small, and when it is more than 0.2, the relative permittivity εr is small.
Both r and the quality factor Q become small, which is not preferable. Therefore, c is preferably in the range of 0.1<b<0.2, more preferably 0.12<c<0.18.

[0011] When w is less than 0.001, the dielectric constant εr
is not large, and if it is 0.25 or more, the quality factor Q decreases, which is not preferable. Therefore, w is 0.001< w
<0.25, more preferably 0.0
1<w<0.2 is preferable. x is less than 0.01 or 0
．． If it is 85 or more, the temperature coefficient τf of the resonance frequency becomes large, which is not preferable. Therefore, x is 0.01<
A range of x<0.85 is suitable, and a range of 0.01<x<0.6 is more preferable. When y is less than 0.01 or more than 0.85, the temperature coefficient of resonance frequency τ
f becomes large, which is not preferable. Therefore, y is preferably in the range of 0.01<y<0.85, more preferably 0.01<y<0.6
Good. If z is less than 0.1 or more than 0.75, the temperature coefficient τf of the resonance frequency becomes large, which is not preferable. Therefore, z is preferably in the range of 0.1<z<0.75, more preferably 0.15<z<0
．． 7 is good.

The dielectric ceramic composition according to the present invention may ultimately be an oxide ceramic composition, and as is commonly done, barium (Ba), lead (PbO), titanium (Ti), etc.
, lanthanum (La), praseodymium (Pr), gadolinium (Gd), etc., or starting materials that become oxides by thermal decomposition of carbonates, basic carbonates, nitrates, hydroxides, organic acid salts, etc. It can be manufactured by a method of mixing and firing. 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 1
It is preferable to carry out the process at about 300°C. Calcining temperature is 90
If the temperature is lower than 0°C, the solid phase reaction due to calcination will not be promoted, and if the calcination temperature exceeds 1300°C, the calcined powder will aggregate and the powder properties will deteriorate, which is not preferable.

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 performed in an atmosphere containing oxygen gas such as an air atmosphere.
It is preferable to carry out the reaction at a temperature of about 1300 to 1600°C.

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 adjustment rods, etc., and has particularly excellent effects when used as a dielectric resonator used in the 0.1 to 4 GHz band.

[0016]

[Examples] The present invention will be explained in detail below with further examples and comparative examples. Examples 1-27, Comparative Examples 1-8. High purity BaCO3, Pb3O4, TiO2,
La2O3, Pr3O11/3, and Gd2O3 powders were weighed to achieve a predetermined composition ratio, and then wet mixed for 20 hours using a ball mill. After drying this slurry by heating, it was calcined in air at a temperature of 1050° C. for 2 hours, and the resulting calcined product was wet-pulverized again for 20 hours using a ball mill. After heating and drying the obtained slurry,
Add an appropriate amount of polyvinyl alcohol and knead, 3
It was granulated using a 2-mesh sieve. Molding pressure of granulated powder 80
Pressure molded at 0 kg/cm2 and heated to temperature 1 in air.
It was baked at 350°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 a Murata Manufacturing Co., Ltd. product (model number: DRG 8553) and a measuring jig (model number: YHP 8510). 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, -30
The temperature coefficient τf was determined by measuring in the range from °C to +80 °C. The experimental results are shown in Table 1. Note that the value of the quality factor Q in Table 1 was converted into a value at 1 GHz using the relational expression fo×Q=constant between the resonance frequency fo and the quality factor Q.

[0018]

[Table 1]

[0019]

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

Claims (1)

[Claims] [Claim 1] Compositional formula a・{(1-w)・BaO
,w・PbO}・b・TiO2・c・{x・
La2O3 ・y ・Pr2O11/3・z ・Gd
2O3 } (where a, b, c, x, y, z are molar ratios, a+b+c=1, 0.1<a<0.2, 0.6<b
<0.8, 0.1<c<0.2, 0.001<w<0.
25, x+y+z=1, 0.01<x<0.85
, 0.01<y<0.85, 0.1<z<0.75
) Dielectric ceramic compositions based on barium, lead, titanium, lanthanum, praseodymium, and gadolinium.