JPH0327509B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is an alumina porcelain composition used in the telecommunications field such as microwave dielectric resonators, microwave integrated circuit boards, packages, microwave waveguides, and high energy physics fields such as microwave transmission windows. relating to things. BACKGROUND ART With the development of communication networks in recent years, the frequency range in use has expanded to include high frequencies. In connection with this, dielectric ceramics are applied to dielectric resonators, microwave integrated circuit boards, impedance matching of various microwave circuits, etc. in the high frequency region. By the way, alumina porcelain has a high high-frequency Q value of around 7000, but the temperature coefficient τ of the resonance frequency is large, and it is impossible to satisfy |τ|≦30ppm/℃, which is desired in the communication field, and is approximately -60ppm/℃. Therefore, it was difficult to use it as a dielectric material. To solve this problem, alumina porcelain was created by blending and sintering calcium titanate, which has a temperature coefficient opposite to that of alumina.
189054) and alumina porcelain blended with strontium titanate and sintered (Japanese Patent Application No. 59-151589) have been proposed. Problems to be solved by the invention However, the alumina porcelain material proposed above has
The temperature coefficient (τ) has a very high dependence on the firing temperature, and a slight change in the firing temperature causes a large change in τ. This has been a major obstacle in the stable production of alumina porcelain having a predetermined temperature coefficient, and it has been desired to solve this problem. Means for Solving the Problems The present invention has been made to solve the above problems, and includes the following: (A) The compounding ratio of the ternary porcelain composition consisting of Al ₂ O ₃ , CaO and TiO ₂ is In the ternary composition diagram (Figure 1) expressed as a ratio, it must be within the range surrounded by the straight line connecting each point below. Al ₂ O ₃ CaO TiO ₂ points 1 98 1 1 point 2 96 2.5 1.5 points 3 94 4 2 points 4 94 3 3 points 5 94 2 4 points 6 96 1.5 2.5 (unit mol%) (B) Al ₂ O ₃ ( _CeO2 (mol%) in relation to (external weight%)
is within the area surrounded by straight lines connecting the points below in the two-component graph (Figure 2).

This is an alumina porcelain composition characterized by satisfying the two conditions shown in [Table]. Here, each component of Al ₂ O ₃ , CaO, and TiO ₂ in FIG. 1 will be explained. As for the composition of Al ₂ O ₃ -CaO-TiO ₂ in Figure 1, as Al ₂ O ₃ becomes richer than point 1, the Q value increases, but τ becomes less than -30 ppm/°C, and line segment 3-4-
If it is poorer than 5, sintering is incomplete, the Q value is less than 4800, and τ exceeds +30 ppm/°C, so none of these are suitable for practical use. Also, line segment 1-2-3 or line segment 5-6-1
On the CaO rich or TiO ₂ rich side, both τ
The absolute value of is greater than 30 ppm/℃, making it unsuitable for practical use. Therefore, in the composition of Al ₂ O ₃ -CaO-TiO ₂ in the present invention, the triangular range surrounded by points 1, 2, 3, 4, 5, and 6 in Fig. 1 corresponds to the temperature coefficient of the resonant frequency of the sintered body. (τ), Q value, and dielectric loss at high frequency are all in a preferable range, but with this alone, it is difficult to obtain a practical product unless the firing temperature dependence of the temperature coefficient (τ) of the resonant frequency is resolved. As mentioned above, this is not possible. In the present invention, in order to improve this point, the problem can be solved by adding a predetermined amount of CeO ₂ as shown in FIG. 2 to the composition. That is, in the present invention, ₃ mol% of Al ₂ O is taken as the horizontal axis and CeO ₂
If the vertical axis is the external weight %, then point 21 in the table below,
22, 23, and 24, and the mole percent of Al ₂ O ₃ is within the range of 94% to 98% (mole fraction) in FIG. In contrast, when the external weight percent of CeO ₂ is below the 22-23 line, the amount of CeO ₂ is insufficient and still
The temperature characteristic (τ) of the resonance frequency is strongly dependent on the firing temperature and is not practical. Also, 21-24
When it is above the line, the amount of CeO ₂ becomes excessive, and while the dependence of τ on the firing temperature improves, it has the disadvantage that τ shifts to a negative value. Figure 3 shows conventional Al ₂ O ₃ −CaO without adding CeO ₂
FIG. 4 is a graph showing the relationship between the firing temperature and Q _and τ of the _{-TiO 2} -based porcelain composition.
- Firing temperature and Q of TiO ₂ - CeO ₂ based porcelain composition,
This is a relationship graph of τ. According to this, in conventional porcelain compositions, the Q value peaks at a certain firing temperature and decreases, and the τ increases in proportion to the firing temperature, but those that satisfy both are ultimately limited to a certain firing temperature. The characteristics are insufficient. On the other hand, in the case of the material according to the present invention, both the Q value and τ are high and flat at a firing temperature above a certain point, so that it is easy to obtain a material preferable as a dielectric material. Examples A ceramic composition according to the present invention and a ceramic composition according to a comparative example were manufactured according to the procedure shown below. Alumina (commercially available, purity 99.995%) 500 Titanium dioxide (special grade reagent) Predetermined amount Calcium carbonate (〃)〃 Cerium oxide (〃)〃 Deionized water 400ml Polyvinyl alcohol 10g More than 20mmφ alumina coccule (purity 99.99%)
Put it into a polyethylene ball mill with 1.0Kg and 50
Mixing time (84RPM). The obtained slurry was freeze-dried and then passed through a 32-mesh sieve to obtain a base powder. Using this base powder, the size is measured at a pressure of 1500Kg/ ^cm2.
A test piece of 14.5φmm x 9.5Lmm was prepared and fired at a predetermined temperature. The size of the fired product is approximately
It became 11.7φmm x 7.6mmL. Next, mirror-finish this to size 11φmm x 7Lmm,
After ultrasonic washing with chlorocene and deionized water for 10 minutes each, the sample was air-dried, and then dried in a desiccator containing silica gel for 15 hours to prepare a test sample. Measurement conditions Method: Dielectric cylinder resonance method Equipment: 8408B manufactured by Yokogawa Heuretsu Card Co., Ltd.
Network analyzer Frequency: 7.0 to 8.0 GHz Temperature coefficient τ of resonance frequency is +20°C to +85°C
The temperature change rate τ of the relative dielectric constant and the thermal expansion coefficient α were measured in the temperature range of , and the value was calculated based on the following equation. τ=−1/2τ−α Note that the ceramic composition of the example according to the present invention is
This is an example of what is within the triangle area surrounded by points 1, 2, 3, 4, 5, and 6 in the figure, and within the area surrounded by points 21, 22, 23, and 24 in Figure 2. , the porcelain composition of the comparative example is outside the above range in FIG. 1 and is surrounded by points 8, 9, 10, 11, 12, and 13,
Does not contain CeO ₂ or is outside the range shown in Figure 2.
CeO ₂ was added. The specific composition and properties are as shown below. However, the characteristic values are measured at =10 GHz, and the preferable characteristics are as follows. Dielectric constant: around 10 Temperature coefficient of resonance frequency |τ|30ppm/℃ No-load Q>4800 Firing temperature range of △τ=1: △τ℃30. Also, the inside and outside of the remarks column indicates what is within and outside the scope of the present invention.

【table】

【table】

[Table] Effects of the invention As can be seen from the above comparative tests, the present invention
The porcelain composition consisting of Al ₂ O ₃ −CaO − TiO ₂ −Ce ₂ O has an excellent dielectric constant of around 10, a temperature coefficient of resonance frequency within the range of −30 to +30, and an unloaded Q of around 5000. In particular, the dependence of the temperature coefficient on the firing temperature is extremely low, which is extremely advantageous for stably producing porcelain having a predetermined temperature coefficient.

[Brief explanation of the drawing]

FIG. 1 shows the components of the porcelain composition of the present invention, Al ₂ O ₃ ,
This is a ternary composition diagram showing the content of CaO and TiC ₂ , and Figure 2 shows the content of CeO ₂ in the porcelain composition of the present invention.
It is a graph showing the addition ratio to Al ₂ O ₃ . Furthermore, FIG. 3 is a graph of the relationship between the firing temperature and Q and τ of the conventional porcelain composition, and FIG. 4 is a graph of the relationship between the firing temperature and Q and τ of the porcelain composition of the present invention.

Claims (1)

[Claims] 1 (A) In a ternary composition diagram in which the blending ratio of a ternary porcelain composition consisting of Al ₂ O ₃ , CaO and TiO ₂ is expressed in mole fraction, a straight line connecting each point below Being surrounded. [Table] (B) CeO ₂ (external weight %) relative to Al ₂ O ₃ (mol %)
is within the area surrounded by the straight line connecting each point below in the two-component graph. An alumina porcelain composition characterized by satisfying the two conditions in [Table].