JPH0415963B2 - - Google Patents

Description

[Detailed description of the invention]

(Technical field) The present invention has a large relative dielectric constant (εr) and no-load Q, and by changing the composition, an arbitrary temperature coefficient (ηf) that is positive or negative around zero can be obtained. The present invention relates to a dielectric ceramic composition. (Technical background) In ceramic capacitors for temperature compensation and dielectric resonators for microwave circuits, dielectric ceramic compositions have large relative dielectric constants (εr) and no-load Q, and the temperature coefficient of resonance frequency (ηf) As such, it is necessary to take into account the temperature coefficient of the metal and obtain any positive or negative temperature coefficient centered around zero. Conventionally, BaO-TiO ₂ type, MgTiO ₃ -CaO type, etc. have been used as such dielectric ceramic compositions. However, when dielectric resonators and capacitors are made with these compositions, when the temperature coefficient (ηf) is around 0 (ppm/℃), the relative dielectric constant (εr) is as small as 20 to 40, making it difficult to use these materials. When a dielectric resonator or the like is created using this method, the disadvantage is that the device becomes larger. (Object of the invention) The object of the invention is to solve these drawbacks,
This relates to the composition of a material that has a large relative dielectric constant (εr) and no-load Q even when the temperature coefficient (ηf) is around 0 (ppm/°C), and will be described in detail below. (Summary of the invention) The present invention provides a method for adding CeO ₂ or Sm ₂ O ₃ of about 10 mol % or less to BaO, TiO ₂ and Lu ₂ O _3.
is added. (Example) As the first example, high purity was used as the starting material.
BaCO ₃ , TiO ₂ , CeO ₂ , and Lu ₂ O ₃ were mixed to have the composition ratios shown in Table 1, and calcined in air at a temperature of 1060° C. for 2 hours.

[Table] The calcined product was wet-pulverized with pure water in a pot mill, dehydrated and dried, a binder was added, and the material was granulated through a 32-mesh sieve. The granulated powder is formed using a mold and a hydraulic press, and the ^diameter is
It was molded into a disk shape of 16 mm and 9 mm thick. The compact was placed in a high-purity alumina box and fired at 1260°C to 1500°C for 2 hours to obtain dielectric ceramics. The dielectric constant (εr) and no-load Q of the obtained dielectric ceramic were determined by measurement using the Hatsuki-Coleman method. The temperature coefficient (ηf) of the resonant frequency was determined from values in the temperature range of -40°C to 80°C based on the resonant frequency at 20°C. The resonant frequency in these measurements was between 3 and 7 GHz. Table 2 shows the results of characteristic measurements of typical dielectric ceramics. In Table 2, the sample numbers marked with * are comparative examples outside the scope of the present invention, and the other samples are examples within the scope of the present invention.

[Table] That is, (BaO) (TiO ₂ ) when _x is less than 77 mol%
If CeO ₂ exceeds 18 mol%, the unloaded Q is too small to use. Moreover, when Lu ₂ O ₃ is less than 2 mol %, the unloaded Q becomes small. (BaO) (TiO ₂ ) _x exceeds 90 mol% CeO ₂ 7
If it is less than mol% or if Lu ₂ O ₃ exceeds 11 mol%, it cannot be measured and cannot be used. Therefore, from a practical point of view (BaO) (TiO ₂ ) _x : 77
~90 mol%, _CeO2 : 7-18 mol%, _{Lu2O3 :} 2
A range of 11 mol % is suitable. Since x = 3.7 to 4.3 mol, BaO: 14.5 to 19.0 mol%,
_TiO2 : 60.7 to 73.0 mol%, _CeO2 : 7 to 18 mol%,
Lu ₂ O ₃ : A range of 2 to 11 mol % is suitable for dielectric ceramics for microwave use. As a second example, chemically high-purity BaCO ₃ , TiO ₂ , Sm ₂ O ₃ , and Lu ₂ O ₃ were wet-processed with pure water in a pot mill so that the composition ratios shown in Table 3 were obtained as starting materials. Mix, dehydrate and dry in air
It was calcined at 1060°C for 2 hours.

[Table] The calcined product was fired in the same manner as in the first example to obtain dielectric ceramics. The dielectric constant and no-load Q of the obtained dielectric ceramic were determined in the same manner as in the first example. Table 4 shows the results of characteristic measurements of typical dielectric ceramics. Sample numbers marked with * in Table 4 are comparative examples outside the scope of the present invention.
The other samples are examples within the scope of the present invention.

[Table] That is, when Sm ₂ O ₃ exceeds 15 mol %, the no-load Q is small and the temperature coefficient is negatively large. When Lu ₂ O ₃ exceeds 10 mol %, the unloaded Q becomes small and the temperature coefficient becomes large. Also, (BaO) (TiO ₂ ) _x
exceeds 90 mol% and Sm ₂ O ₃ is less than 7 mol%, and (BaO) (TiO ₂ ) _x is less than 78 mol% and Lu ₂ O ₃
If it exceeds 10 mol%, the no-load Q will be small and the temperature coefficient will also be large. When Lu ₂ O ₃ is 2 mol% or less,
Cannot be used due to small no-load Q. Therefore, from a practical point of view (BaO) (TiO ₂ ) _x : 78
~90 mol% _{, Sm2O3} : 7-15 mol%, _Lu2O3 : ₂
A range of 10 mol % is suitable. From x=3.7-4.3, BaO: 15.0-19.0 mol%, _TiO2 : 61.5-73.0
Mol%, Sm ₂ O ₃ : 7 to 15 mol %, Lu ₂ O ₃ : 2 to 10
A range of mol % is suitable for dielectric ceramics for microwave use. (Effects of the Invention) The present invention has a large relative permittivity εr and no-load Q in the microwave region, and the temperature coefficient can be changed depending on the composition. It can be used as dielectric ceramics for temperature compensation capacitors, etc.

Claims (1)

[Claims] 1. Microwave dielectric ceramics comprising 14.5 to 19.0 mol% of BaO, 60.7 to 73.0 mol% _of TiO2, 7 to 18 mol% of CeO2, and ₂ to ₁₁ mol% of _Lu2O3 . 2 Dielectric ceramic for microwaves consisting of 15.0 to 19.0 mol% _BaO , 61.5 _to 73.0 mol% TiO2, 7 to 15 mol _% Sm2O3 _, and ₂ to 10 mol% Lu2O3.