KR950008601B1 - Composition of deelectric substance - Google Patents

Abstract

The magnetic composition of dielectric ceramics for temperature compensation comprises 70 mol% titanium dioxide, 20 mol% barium carbonate, 5-9 mol% neodymium oxide and 1-5 mol% dysprosium oxide. The dielectric ceramics is manufactured by sintering the molded body of this composition at 1,250 - 1,300 deg.C. The dielectric ceramics body of this composition has properties of high permittivity, low temperature coefficient, good quality coefficient in high frequency, high insulation resistance and low sintering temperature.

Description

Temperature Compensation Dielectric Ceramic Composition

The present invention relates to a temperature compensating dielectric ceramic composition having high dielectric constant, good quality factor Q at high frequency, high insulation resistance, and particularly small temperature coefficient of capacitance.

A dielectric ceramic composition for a prior art temperature compensation, such as _{MgTiO 3, CaTiO 3, SrTiO 3} , CaTiO 3 -La 2 O 3, 2TiO 2 -MgTiO 3, BaO-TiO 2 -Nd 2 O 3 has a number known. It is well known that their dielectric constant is 15 to 280 and the temperature coefficient of capacitance is in the range of +100 to -450 ppm / ° C.

However, the biggest disadvantage of these systems is that when the temperature coefficient is small, it is difficult to obtain high dielectric constant and the dielectric loss at high frequency tends to be worsened.

Recently, magnetic compensation capacitors have been used in IFT (intermediate frequency) circuits such as color TVs.The temperature coefficient of magnetic capacitors should be small (-350 ~ + 1000ppm / ℃), and the dielectric loss is small at high frequencies. Therefore, a dielectric material having a high dielectric constant is needed. In addition, for dielectric resonators, it is required that the temperature loss of the resonant frequency be linear while the dielectric loss of the microwave frequency band is small.

The present invention aims to eliminate the disadvantages of the prior art and to provide a temperature compensation dielectric self-composition having a small temperature coefficient, a high dielectric constant, and a low dielectric loss at high frequencies.

An object of the present invention is to develop a dielectric ceramic composition for temperature compensation having a high dielectric constant of 80 or more at room temperature and having a temperature coefficient of capacitance within ± 60 ppm / ° C., having a good quality coefficient and insulation resistance.

In order to achieve the above object, the present invention uses titanium dioxide (TiO ₂ ) as a main component, 70 mol% of titanium dioxide (TiO ₂ ) as a first component, 20 mol% of barium carbonate (BaCO ₃ ) as a second component, and a third component. 5 to 9 mol% of neodymium oxide (Nd ₂ O ₃ ), the fourth component is characterized in that consisting of 1 to 5 mol% of dysprosium oxide (Dy ₂ O ₃ ).

Barium carbonate forms barium titanate (BaTiO ₃ ) together with titanium dioxide to contribute to high dielectric constant. Increasing the amount of barium carbonate increases the dielectric constant and moves the temperature coefficient to the negative side, decreasing decreases the temperature coefficient to the positive side and decreases the dielectric constant.

Titanium dioxide acts as a sintering aid and contributes to the temperature coefficient. When the amount of titanium dioxide exceeds 80 mol%, the temperature coefficient is largely shifted to the positive side, and if it is 60 mol% or less, the dielectric constant is decreased and the temperature coefficient is largely shifted to the negative side.

Neodymium oxide and dysprosium oxide contribute to the improvement of the quality coefficient Q value and the temperature coefficient. When 10 mol% or more, the temperature coefficient moves largely to the negative side, and when it is 5 mol% or less, it is difficult to maintain good quality.

When the composition is sintered at a sintering temperature in the range of 1250 ~ 1300 ℃ can obtain a dielectric constant of 80 or more and a quality factor of 2000 or more.

Hereinafter, an embodiment according to the present invention will be described in detail.

Titanium dioxide, barium carbonate and neodymium oxide, and dysprosium oxide are weighed as shown in Table 1 and mixed with deionized water. Mixing uses zirconia balls and jars, using a ball milling method. The dried powder is calcined at 1100 ° C. for 2 hours and mixed in polyvinyl alcohol and mortar. The mixed material is molded into disc-shaped specimens of 15 mm diameter using a mold and hydraulic press. The pressure at the time of molding was 1 ton / ㎠ and the thickness of the specimen after molding was 1.8 ~ 2mm. The molded specimen is placed in a zirconia setter and sintered in an electric furnace in an air atmosphere. Sintering temperature and sintering time are shown in Table 1. The silver electrode is coated on both sides of the sintered specimen in a circular shape of 10 mm diameter by printing coating method and then heat treated to measure the electrical properties. Dielectric constants, quality coefficients, and capacitance temperature coefficients are measured using an impedance / gain phase analyzer (HP4194A), and insulation resistance is measured using a megaohmmeter. The dielectric constant is measured at 1 MHz and 1 V, and the insulation resistance is measured after 1 minute passes with a DC voltage of 50 V applied. Table 2 shows the dielectric properties of the sintered body. Dielectric constant of 80 or higher was shown at sintering temperature of 1250 ℃ or higher, and the temperature coefficient was also excellent characteristic within -60ppm / ℃. The insulation resistance was found to be 4.3 × 10 ¹⁴ Ω · cm and the particle size was uniform to 2㎛ or less, which is suitable for use as a material for temperature compensation.

TABLE 1

TABLE 2

According to the present invention, a dielectric material of 80 or more at room temperature was obtained. These dielectrics exhibit a high quality factor Q of greater than 2000 and particularly good temperature characteristics of up to -21 ppm / ° C. Therefore, it can be used to manufacture capacitors using temperature compensation dielectrics and EMI (electromagnetic interference) filters for noise removal. In addition, an inexpensive silver alloy can be used as an electrode material instead of expensive Pd or Pt material, thereby reducing manufacturing process costs.

Claims (2)

In the dielectric ceramic composition, 70 mol% titanium dioxide (TiO ₂ ) as the first component, 20 mol% barium carbonate (BaCO ₃ ) as the second component, and 5 to 9 mol% neodymium oxide (Nd ₂ O ₃ ) as the third component 1 to 5 mol% of dysprosium oxide (Dy ₂ O ₃ ) is added as a fourth component. The dielectric ceramic composition according to claim 1, which is sintered at a temperature of 1250 to 1300 ° C.