JPH09221361A - Dielectric ceramic composition for temperature compensation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a large dielectric constant by forming a ceramic composition consisting of PbO, ZrO2 , MgO and TiO2 and expressed by a specified formula. SOLUTION: Powdery starting materials such as PbO, ZrO2 , MgO and TiO2 are blended in a prescribed ratio, and water is added and the mixture is subjected to wet mixing with a ball mill, etc., and the mixture is dehydrated, dried and calcined at about 1000-1100 deg.C, then the water is added and the mixture is ground and mixed with the ball mill, dehydrated and dried. Then, an org. binder such as PVA is added to the powdery mixture and compacted, and the compact is burned at about 1,200-1,300 deg.C for an order of 2hr and a dielectric ceramic composition for temp. compensation having a composition expressed by the formula xPbZrO3 .(1-x)MgTiO3 (0.15<=x<=0.3) is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature compensating dielectric ceramic composition, and more particularly to a temperature compensating dielectric ceramic composition useful as a dielectric material for a multilayer capacitor.

[0002]

2. Description of the Related Art Temperature-compensating dielectric ceramic capacitors are widely used in communication equipment and the like. Dielectric materials used for such applications generally have a large dielectric constant, a large Q (that is, a small dielectric loss), and a dielectric constant temperature coefficient of -7.
Characteristics such as in the range of 50 to +100 ppm / ° C are required.

Heretofore, CaTiO ₃ —MgTiO ₃ based materials and the like have been known as a temperature compensating dielectric porcelain composition. This material has a high Q with a dielectric constant of 20-30.
(Usually about 10,000). The temperature coefficient of dielectric constant is about -30 to +30 ppm / ° C.

By the way, at present, among communication devices, a crystal oscillator is used in a cellular phone or the like, which has undergone remarkable technological innovation. This oscillator uses a crystal oscillator, for example -2
A stable oscillation output can be obtained in the temperature range of 0 to + 70 ° C. Since the crystal oscillator used for this has variations in the temperature characteristics of individual products depending on the cut state, the frequency temperature characteristics are controlled using capacitors and thermistors.

[0005]

The resonance frequency temperature characteristic of a crystal oscillator can be compensated by capacitors having different positive or negative temperature coefficients. However, conventionally, there is no capacitor having a large positive temperature coefficient of the dielectric constant, so that the crystal oscillator that can be compensated is limited, which lowers the yield of the crystal oscillator. Therefore, development of a temperature compensating dielectric having a large positive temperature coefficient of dielectric constant has been strongly desired.

The present invention has been made in view of the above conventional circumstances, and has a large dielectric constant, a large Q (small dielectric loss), a positively large temperature coefficient of the dielectric constant, and It is an object of the present invention to provide a temperature-compensating dielectric ceramic composition whose value can be freely controlled.

[0007]

The dielectric ceramic composition for temperature compensation according to the present invention comprises PbO, ZrO ₂ , MgO and TiO.
_A porcelain composition consisting of ₂ , characterized by being represented by the following composition formula:

XPbZrO _3. (1-x) MgTiO ₃
(However, 0.15 ≦ x ≦ 0.3) As represented by the above composition formula, PbO, ZrO ₂ , Mg
By mixing O and TiO ₂ in a predetermined ratio, Q
It is possible to obtain a temperature-compensating dielectric porcelain having a large value and having a positively large value of the temperature coefficient of the dielectric constant.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The dielectric ceramic composition for temperature compensation of the present invention comprises
PbO, ZrO _2, consists of MgO and TiO _2, when expressed the composition and wherein _{xPbZrO 3 · (1-x)} MgTiO 3, which value of x is in the range of 0.15 ≦ x ≦ 0.3 Is. If x is out of this range, the sinterability of the dielectric ceramic and the electrical characteristics such as the dielectric constant, the dielectric loss and the insulation resistance will be poor. That is, in the above composition formula, if x is smaller than 0.15, a firing temperature exceeding 1300 ° C. is required and the sinterability is deteriorated. Also, x is 0.
If it is larger than 3, the value of the insulation resistance is smaller than 10 ¹¹ Ω, and good characteristics cannot be obtained.

To manufacture such a temperature-compensating dielectric ceramic composition of the present invention, for example, lead oxide (PbO, Pb) is used.
₂ O, PbO ₂ , Pb ₂ O ₃ , Pb ₃ O ₄ ), zirconium oxide (ZrO ₂ ), magnesium oxide (MgO),
Titanium oxide (TiO ₂ , TiO, Ti ₂ O ₃ ) powder is weighed so as to have a predetermined ratio and sufficiently mixed using a wet ball mill or the like. Next, after drying this mixture, if necessary, it is calcined in the range of 1000 to 1100 ° C. for several hours. The obtained calcined product is pulverized by a wet ball mill or the like. After drying the calcined powder obtained by the pulverization, an appropriate organic binder such as polyvinyl alcohol is added to form granules, and the granules are pressed into a predetermined shape and then fired. This firing is performed in a temperature range of 1200 to 1300 ° C. for about 0.5 to several hours. (Of course, these production conditions are the most suitable numerical values, and the porcelain composition of the present invention may be produced under the conditions or methods other than the above.)

[0012]

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

Example 1 PbO, ZrO ₂ , MgO and TiO ₂ as starting materials
Were weighed so that the compounding ratios shown in Table 1 were obtained, and wet-mixed with pure water for about 20 hours in a ball mill. Then, after dehydrating and drying this mixture, 1050 to 1
The mixture was calcined while being kept at 100 ° C. for 2 hours, again wet-pulverized together with pure water for about 20 hours in a ball mill, then dehydrated and dried.

An ethanol solution of polyvinyl butyral (binder) was added to the obtained powder, and the molding pressure was about 2 t / c.
At m ^3, it was pressed into a disk having a diameter of about 15 mm and a thickness of about 0.7 mm. This molded product was held at about 600 ° C. for 1 hour to remove the binder, and then 1200 magnesia setter.
Baking at a temperature of ~ 1300 ° C for 2 hours.

750 silver electrodes are provided on both surfaces of the obtained sintered body.
It was baked at ℃ to make a parallel plate capacitor, and its electrical characteristics were examined. Table 1 shows the measurement results of the electrical characteristics of the obtained sample.

The dielectric constant was measured using "LF Impedance Analyzer Model 4192A" manufactured by YHP at a measurement frequency of 1 MHz, a measurement voltage of 1.0 Vrms, and a temperature of 25 ° C. Q is YHP's "Q meter model 4
"342A" was used for measurement at a measurement frequency of 1 MHz and a temperature of 25 ° C. Also, the insulation resistance is "Analog I" manufactured by YHP.
R meter 4329A "was used to measure the value after 1 minute at a temperature of 25 ° C and an applied voltage of 100V. The temperature coefficient of the dielectric constant was calculated from the following formula from the capacitances of the capacitors measured at 25 ° C. and 85 ° C., respectively.

[0017]

[Equation 1]

[0018]

[Table 1]

As is clear from Table 1, the temperature-compensating dielectric ceramic compositions (Sample Nos. 2 to 7) within the scope of the present invention are:
Dielectric constant is large, Q is large, and temperature coefficient of dielectric constant is +4
It is a high-performance dielectric having various values of 20 ppm / ° C. or more, which are positively large.

[0020]

As described above, the temperature-compensating dielectric ceramic composition of the present invention has a large dielectric constant and a large Q, and
It has a positively large temperature coefficient of permittivity whose value can be freely controlled. Therefore, by using the capacitor using the dielectric ceramic composition for temperature compensation of the present invention, it becomes possible to perform temperature compensation even for a crystal oscillator which has been conventionally impossible to be temperature compensated. Excellent effects such as improvement in yield and reduction in manufacturing cost can be expected.

Claims (1)

[Claims] 1. PbO, ZrO ₂ , MgO and TiO ₂
A dielectric porcelain composition for temperature compensation, which is represented by the following composition formula: _{xPbZrO 3 · (1-x)} MgTiO 3 ( However,
0.15 ≦ x ≦ 0.3)