JPH0737424A - Dielectric porcelain composition - Google Patents

Abstract

PURPOSE:To provide a dielectric ceramic composition which has a high dielectric constant, a high Q-value, and a good stability of taur. CONSTITUTION:This dielectric ceramic composition consists of barium, titanium, samarium, neodium, praseodymium, and oxygen, as shown in the composition formula: xBaO.yTiO2.z[(1-m-n(Sm2O3.mNd2O3.nPr2O11/3] (where 0.15<=x<=0.25, 0.725<y<=0.85, 0<z<0.025, 0<=m<1, and 0<=n<1, and m and n cannot be 0 at a time).

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 composed of barium, titanium, samarium, neodymium, praseodymium and oxygen which is suitable as a dielectric resonator material. The dielectric ceramic composition of the present invention can be used not only as a dielectric resonator material but also as, for example, a microwave IC substrate, a dielectric adjusting rod, or the like.

[0002]

2. Description of the Related Art In recent years, with the integration of microwave circuits, a compact and high-performance dielectric resonator is required. The dielectric ceramic composition used for such a dielectric resonator has a large relative permittivity ε _r , stability of the temperature coefficient τ _f of the resonance frequency, and linearity of the temperature characteristic of the resonance frequency. Characteristics such as excellent and large no-load Q are required.

As such a dielectric ceramic composition,
It is known that TiO ₂ , BaO—TiO ₂ or the like is the main component, but it is difficult to put into practical use because of its large temperature coefficient and large dielectric loss in the microwave band.

A proposal for a BaO--TiO ₂ --Sm ₂ O ₃ -based dielectric ceramic composition (Japanese Patent Publication No. 59-375).
No. 26), but a sufficiently large Q value has not been obtained.

Furthermore, Ba (Mg _1/3 Ta _2/3 ) O
₃ system, Ba (Zn _1/3 Ta _2/3 ) O ₃ system, Ba (Zn
Dielectric porcelain compositions having a perovskite structure such as _1/3 Nb _2/3 ) O ₃ system are also known, but these have a low relative permittivity, so that they are resonators in the 0.1-5 GHz band, for example. Has the drawback of becoming too large.

[0006]

An object of the present invention is to provide a dielectric ceramic composition suitable as a dielectric resonator material, particularly as a dielectric resonator material used in the 0.1 to 5 GHz band. Another object of the present invention is to provide a dielectric ceramic composition having a high dielectric constant, a large Q, and a good stability of ε _r .

[0007]

Among the many constituent elements used in dielectric porcelain compositions, we have identified a combination of barium, titanium, samarium, neodymium, praseodymium and oxygen. It was found that the above object can be achieved by the porcelain composition of

[0008] The present invention is a composition formula xBaO · yTiO ₂ ·
z [(1-m-n) Sm 2 O 3 · mNd 2 O 3 · nPr
₂ O _11/3 ] (wherein 0.15 ≦ x ≦ 0.25, 0.72
5 <y ≦ 0.85, 0 <z <0.025, 0 ≦ m <1,
0 ≦ n <1. However, m and n are not 0 at the same time. )
Represented by barium, titanium, samarium, neodymium,
The present invention relates to a dielectric ceramic composition composed of praseodymium and oxygen.

Since the dielectric ceramic composition of the present invention has a large relative permittivity, the resonator can be downsized and the unloaded Q also becomes large. Further, the temperature coefficient τ _f of the resonance frequency is small.
In the present invention, when the molar fraction of BaO is larger than 0.25 or the molar fraction of TiO ₂ is smaller than 0.725, the temperature coefficient τ _{f of the} resonance frequency becomes large.
The mole fraction of O and TiO ₂ is limited to the above range. Further, if the _sum of the mole fractions of Sm ₂ O ₃ , Nd ₂ O ₃ and Pr ₂ O _11/3 is more than 0.025, the unloaded Q becomes small, so Sm ₂ O ₃ , Nd ₂ O ₃ and Pr ₂ O
Addition of a mole fraction of _11/3 is limited to the above range.
If Sm ₂ O ₃ is not contained, the temperature coefficient τ _{f of the} resonance frequency becomes large, so m and n are limited to the above range. According to the present invention, since the contents of samarium oxide, neodymium oxide and praseodymium oxide are small, it is possible to manufacture at low cost.

An example of a suitable method for producing the dielectric ceramic composition of the present invention will be described below. Starting materials of barium carbonate, titanium oxide, samarium oxide, neodymium oxide and praseodymium oxide are wet-mixed in predetermined amounts with a solvent such as water or alcohol. Then, after removing water, alcohol, etc.,
It is crushed and calcined in an oxygen-containing gas atmosphere (for example, an air atmosphere) at 900 to 1100 ° C. for about 2 hours. The calcined product thus formed is crushed, mixed with an organic binder such as polyvinyl alcohol to be homogenized, dried and crushed, and pressure-molded (pressure 100 to 1000 Kg / c).
m ² ). Then, by firing this molded product at 1200 to 1400 ° C. in an oxygen-containing gas atmosphere such as air, the dielectric ceramic composition represented by the above composition formula is obtained.

The dielectric ceramic composition thus obtained is processed as it is, or if necessary, processed into an appropriate shape and size to obtain a dielectric resonator, a dielectric substrate for microwave IC, a dielectric adjusting rod. Etc., and particularly when used as a dielectric resonator used in the 0.1 to 5 GHz band, excellent effects are exhibited.

The raw materials for barium, titanium, samarium, neodymium and praseodymium are BaCO ₃ ,
In addition to TiO ₂ , Sm ₂ O ₃ , Nd ₂ O ₃ , Pr ₂ O _{11/3 and the} like, it is possible to use carbonates and hydroxides which become oxides during firing.

[0013]

EXAMPLES The present invention will be described more concretely with reference to the following examples. Example 1 Barium carbonate (BaCO ₃ ) powder 0.200 mol, titanium oxide (TiO ₂ ) powder 0.780 mol, samarium oxide (Sm ₂ O ₃ ) powder 0.010 mol, neodymium oxide (Nd ₂ O ₃ ) powder 0.010 mol was put in a ball mill together with ethanol and wet-mixed for 12 hours. The mixture was taken out of the ball mill, the solvent ethanol was evaporated, and the mixture was ground with a muller for 1 hour to obtain 0.200 BaO.
780TiO ₂ / 0.010Sm ₂ O ₃ / 0.010N
A calcined powder having a composition of d ₂ O ₃ was obtained.

Then, an appropriate amount of polyvinyl alcohol solution was added to the calcined powder and mixed uniformly, and then the diameter was 15 mm.
A pellet having a diameter of φ and a thickness of 5.5 mm was formed, fired at 1250 ° C. for 2 hours in an air atmosphere, and sintered to obtain a dielectric ceramic composition of the present invention. The porcelain composition thus obtained was cut into an appropriate size and then measured by a dielectric resonance method to obtain an unloaded Q and a relative permittivity ε _r at a resonance frequency f ₀ (2 to 6 GHz). The temperature dependence of the resonance frequency was measured in the range of -40 to 50 ° C to obtain the temperature coefficient τ _f . The results are shown in Table 2.

Examples 2 to 14 Dielectric materials were prepared in the same manner as in Example 1 except that the mixing ratio of barium carbonate, titanium oxide, samarium oxide, neodymium oxide and praseodymium oxide in Example 1 was changed as shown in Table 1. A porcelain composition was produced and the characteristics were measured as in Example 1. The results are shown in Table 2. Those marked with * in the table are comparative examples outside the scope of the present invention.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

According to the present invention, a dielectric ceramic composition having a high dielectric constant, a large Q, and a good stability of τ _f can be obtained.

Claims (1)

[Claims] 1. A composition formula xBaO.yTiO ₂ .z [(1-
_{m-n) Sm 2 O 3} · mNd 2 O 3 · nPr 2 O 11/3 ]
(In the formula, 0.15 ≦ x ≦ 0.25, 0.725 <y ≦
0.85, 0 <z <0.025, 0 ≦ m <1, 0 ≦ n <
It is 1. However, m and n are not 0 at the same time. ) A dielectric ceramic composition composed of barium, titanium, samarium, neodymium, praseodymium, and oxygen.