JP2005187272A - Dielectric ceramic composition and its production method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a dielectric ceramic composition having a very high Qf product, in which the dielectric constant and quality factor Qf product are enhanced; and to obtain a method for producing the same. <P>SOLUTION: The dielectric ceramic composition contains, as main components, ZrO<SB>2</SB>, SnO<SB>2</SB>and TiO<SB>2</SB>, and in the composition, the compositional ratios of the main components are given by following formula: xZrO<SB>2</SB>-ySnO<SB>2</SB>-zTiO<SB>2</SB>(wherein, x+y+z=100 mol%). The compositional ratios are as follows: 31≤x≤42 and 9≤y≤18, and the remainder is TiO<SB>2</SB>. Further, when the addition amounts of La<SB>2</SB>O<SB>3</SB>, NiO and Ta<SB>2</SB>O<SB>5</SB>to the total weight of the main components are defined as u, v and w wt.%, respectively, u is ≥0.1 and ≤0.5, v is ≥0.1 and ≤0.5 and w is ≥0.1 and ≤0.5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a dielectric ceramic composition suitable for use in a dielectric filter or the like mainly used in a mobile phone or a wireless LAN, and a method for producing the same.

  With the progress of high-frequency transmission technologies such as cellular phones and wireless LANs, there are increasing demands for high performance and miniaturization of filter elements and oscillation elements in the microwave and millimeter wave regions. Many filter elements and oscillation elements take the form of dielectric resonators. Therefore, improvement of the characteristics of the dielectric material is extremely important for improving the performance of the high frequency device. The technical requirements for the dielectric material include the following three.

  First, a dielectric material having a high relative dielectric constant is required. This is because the size of the dielectric resonator is proportional to the reciprocal of the square root of the relative permittivity of the dielectric material.

  Second, a low-loss dielectric material is required in the high frequency region. The loss of the dielectric is represented by the dielectric loss tan δ, and the higher the quality factor Qf product obtained by multiplying the reciprocal number by the resonance frequency f, the better the loss of the high-frequency element is reduced.

  Thirdly, there is a demand for the development of a dielectric material whose temperature coefficient of the resonance frequency of the dielectric resonator is close to zero and can be arbitrarily controlled. This is because it is generally required that the frequency characteristic change of the element with respect to environmental temperature fluctuation is small.

Here, currently, a dielectric ceramic composition having a relative dielectric constant of about 38 is used. Of these dielectric ceramic compositions, those having a Qf product of about 37 THz have been put into practical use, but this is not satisfactory. For high performance, a dielectric material having a Qf product improved by 20% or more is required. Further, it is necessary that the temperature coefficient τf of the resonance frequency is near zero. On the other hand, ZrO ₂ , SnO ₂ and TiO ₂ are the main components, and La ₂ O ₃ and ZnO (Patent Document 1), ZnO and Co ₂ O ₃ (Patent Document 2), and MnO ₂ (Patent Document 3) as additives. ) And the like are known.

When La ₂ O ₃ and ZnO are added, the Qf product is 44 THz or less, and when ZnO and Co ₂ O ₃ are added, the Qf product is 35 THz to 55 THz, but Co ₂ O ₃ is contained in the sintering furnace. There is a manufacturing problem that a dedicated sintering furnace is required to contaminate the steel. Further, it is known that when MnO ₂ is added, the Qf product becomes as small as 18 THz or less. These known dielectric ceramic compositions have the problem that they do not satisfy the above three characteristics, or the problem that they cannot be manufactured at low cost. Application of was difficult. Further, when the size of the dielectric ceramic composition is 20 mm or more and the height is 20 mm or more in the conventional manufacturing method, there is a problem that the Qf product becomes 20 or less.

  In addition, a sintered body used for a dielectric resonator filter of a radio base station such as a mobile phone base station has a large volume of 20 mm in diameter and 20 mm in height or more in terms of a hollow cylinder. In such a large-sized sintered body, the difference between the sintered body surface and the internal sintered state tends to occur with respect to the degree of evaporation of trace elements and the frequency of occurrence of oxygen defects. This causes the Qf product deterioration. For this reason, even when production is performed using a dielectric ceramic composition having a high Qf product, there has been a problem that the deterioration of the Qf product proceeds as the sintered body becomes larger.

JP 52-17699 JP 52-17698 A JP-A-6-215626

As a general property of dielectric materials, it is known that as the relative dielectric constant increases, the Qf product decreases. However, in order to improve the performance of a high-frequency device, a dielectric ceramic having a high Qf product, a large relative dielectric constant, and a small absolute value of the temperature coefficient of the resonance frequency when used as a dielectric resonator. A composition is needed. Here, the conventional dielectric ceramic composition to which Co ₂ O ₃ is added has a problem that the inside of the sintering furnace is contaminated. In addition, when manufacturing a large-sized sintered body of a dielectric ceramic composition (20 mm or more in diameter and 20 mm or more in height when converted to a non-hollow cylindrical shape), the Qf product is likely to deteriorate. There is a need for a manufacturing method that can be obtained at low cost.

  An object of the present invention is to increase the relative dielectric constant and the quality factor Qf product in a large-sized sintered body with a dielectric ceramic composition without contaminating the inside of the sintering furnace, and to provide a dielectric ceramic having a high Qf product. It is to provide a method for producing the composition and the porcelain composition.

In the ZrO ₂ —SnO ₂ —TiO ₂ ceramic dielectric, the present invention selects a main component blending ratio, a kind of additive, and an addition amount that provide a high relative dielectric constant and a Qf product suitable as a microwave dielectric. The dielectric ceramic composition obtained in this way and this raw material powder or in a mixed atmosphere of nitrogen gas, argon gas, air, etc. and oxygen are sintered at a sintering temperature of 1300 ° C. to 1450 ° C. with an oxygen concentration of 30% or more. In addition, it is a dielectric ceramic composition for microwaves formed by performing slow cooling in a specific temperature range in the cooling process.

More specifically, when the ZrO ₂ content is 42 mol% or more or 31 mol% or less in the main component, the Qf product is too small, which is not desirable. When the SnO ₂ content is 9 mol% or more, the absolute value of the temperature coefficient τf of the resonance frequency is too large, which is not desirable. Further, SnO ₂ content of the following cases 18 mol%, undesirably Qf product is too small. When TiO ₂ is 55 mol% or more or 47 mol% or less, the absolute value of the temperature coefficient τf of the resonance frequency is too large, which is not desirable.

In the additive, La ₂ O ₃ has a sintering promoting effect, and by adding 0.1 wt% or more with respect to the total weight of the main component, sintering at 1400 ° C. or less becomes possible. NiO has a sintering promoting effect. By adding 0.1 wt% or more with respect to the total weight of the main component, it becomes possible to sinter at 1400 ° C. or less, and the Qf product is lower than that in the case where NiO is not added. The improvement is remarkable. Ta ₂ O ₅ has an effect of increasing the Qf product, and the addition of 0.1 wt% or more with respect to the total weight of the main component improves the Qf product by 20% or more. On the other hand, when the added weight in each of La ₂ O ₃ , NiO, and Ta ₂ O ₅ exceeds 0.5 wt%, the Qf product is lowered. As described above, the addition amount of each of La ₂ O ₃ , NiO, and Ta ₂ O ₅ is limited to 0.1 wt% or more and 0.5 wt% or less. By simultaneously adding and adjusting La ₂ O ₃ , NiO, and Ta ₂ O ₃ within this range, the relative dielectric constant becomes about 38 to 42, and the temperature coefficient τf of the resonance frequency becomes near zero, which is suitable for a dielectric filter. In particular, it has been found that a dielectric ceramic composition capable of obtaining a particularly high Qf product can be obtained.

That is, in a dielectric ceramic composition containing ZrO ₂ , SnO ₂ , and TiO ₂ as main components, when the main component composition ratio is expressed as xZrO ₂ · ySnO ₂ · zTiO ₂ (x + y + z = 100 mol%), 31 mol% ≦ x ≦ 42 mol%, 9 mol% ≦ y ≦ 18 mol%, the balance is TiO ₂ , and the addition amount of La ₂ O ₃ , NiO, Ta ₂ O ₅ with respect to the total weight of the main components is u, v, w, wt%, respectively. Where 0.1 wt% ≦ u ≦ 0.5 wt%, 0.1 wt% ≦ v ≦ 0.5 Wt%, and 0.1 wt% ≦ w ≦ 0.5 Wt%. A composition can be obtained.

  In sintering this dielectric ceramic composition, the temperature range is from 1300 ° C. to 1450 ° C. with an oxygen concentration of 30% or more in an oxygen gas alone or a mixed atmosphere of nitrogen gas, argon gas, air and the like. It has been found that a larger relative dielectric constant can be obtained by sintering at a temperature higher than that in the case where the oxygen concentration in the sintering atmosphere is 21% (in the air).

  Further, when sintering a large-sized sintered body of the dielectric ceramic composition according to the present invention (diameter 20 mm or more, height 20 mm or more in terms of a non-hollow cylindrical shape), when sintering is finished and cooling is performed. It has been found that a high Qf product can be stably obtained by performing slow cooling at a cooling rate corresponding to 100 ° C./hour or less in the temperature range of 1150 ° C. or higher in terms of constant speed cooling. The slow cooling here may be constant temperature holding, multistage cooling, or non-constant cooling. In particular, it has been found that the effect is great if the slow cooling temperature is slowed down for a cooling time of 1225 ° C. or higher and 1300 ° C. or lower during cooling.

  By using the above manufacturing method, it is possible to achieve simultaneous improvement of relative permittivity and Qf product, which is generally difficult. At the same time, it is possible to prevent the deterioration of the Qf product when manufacturing a large sintered body having a diameter of 20 mm and a height of 20 mm or more in terms of a cylindrical shape, which is difficult with the prior art. When the volume of the sintered body is small, it is easy to manufacture without deteriorating the Qf product inherent in the dielectric ceramic composition, and atmospheric sintering with the lowest manufacturing cost is a preferable manufacturing method. On the other hand, when manufacturing a large-sized sintered body having a diameter of 20 mm and a height of 20 mm or more in terms of a non-hollow cylindrical shape, the manufacturing method according to the present invention does not require a special sintering furnace, and can reduce the Qf product at low cost. Deterioration can be prevented.

According to the present invention, in a dielectric ceramic composition xZrO ₂ .ySnO ₂ .zTiO ₂ (x + y + z = 100 mol%) mainly composed of ZrO ₂ , SnO ₂ and TiO ₂ , the composition ratio is 31 ≦ x ≦ 42, When 9 ≦ y ≦ 18, the balance is TiO ₂ , and the addition amounts of La ₂ O ₃ , NiO, and Ta ₂ O ₅ with respect to the total weight of the main components are expressed as u, v, w, and wt%, respectively, 0. A raw material powder satisfying 1 ≦ u ≦ 0.5, 0.1 ≦ v ≦ 0.5, and 0.1 ≦ w ≦ 0.5 is obtained with an oxygen concentration of 30% or higher in an oxygen gas alone or in a mixed atmosphere. The relative dielectric constant and the quality factor Qf product can be increased by sintering in a temperature range of 1 to 1450 ° C., and more preferably by performing slow cooling (including multi-stage cooling) in a specific temperature interval after the sintering is completed. it can.

  According to the present invention, a dielectric ceramic having a high Qf product can be obtained by increasing the relative permittivity and the quality factor Qf product in a large sintered body of a dielectric ceramic composition without contaminating the inside of the sintering furnace. Compositions and methods of making the same can be provided.

In order to obtain the dielectric ceramic composition according to the present invention, for example, in a dielectric ceramic composition xZrO ₂ .ySnO ₂ .zTiO ₂ (x + y + z = 100 mol%) mainly composed of ZrO ₂ , SnO ₂ , TiO ₂ , The composition ratio is 31 ≦ x ≦ 42, 9 ≦ y ≦ 18, the balance is TiO ₂ , and the addition amounts of La ₂ O ₃ , NiO, Ta ₂ O ₅ with respect to the total weight of the main components are u, v, w, respectively. , Wt%, 0.1 ≤ u ≤ 0.5, 0.1 ≤ v ≤ 0.5, 0.1 ≤ w ≤ 0.5 compositional raw material powder blended, wet mixed, dehydrated After the treatment, calcination is performed at 1000 to 1300 ° C. for 2 to 10 hours. After pulverization and granulation, it is molded into a required shape and debindered. This is sintered in a temperature range of 1300 ° C. to 1450 ° C. with an oxygen concentration of 30% or more in an oxygen gas alone or in a mixed atmosphere. Keep constant temperature or slowly cool in the range. The slow cooling here includes multi-stage cooling in a temperature region of 1150 ° C. or higher, or constant temperature holding. During sintering, the relative permittivity of the sintered body increases as the oxygen concentration is higher than 30%. On the other hand, slow cooling mainly contributes to the improvement of the Qf product.

  In the present invention, it is desirable to combine the oxygen concentration during sintering with 30% or more and the constant temperature holding or slow cooling in the temperature range of 1150 ° C. or higher after sintering. This is a case where the oxygen concentration is set to 30% or higher during sintering, and when annealing is not performed in a temperature region of 1150 ° C. or higher after sintering, Qf is compared with sintering in the atmosphere. This is because the product may not improve. This tendency is particularly noticeable when obtaining a large-sized sintered body having a diameter of 20 mm or more and a height of 20 mm or more in terms of a non-hollow cylindrical shape mounted on a dielectric filter or the like for a radio communication base station. Become prominent. In such a case, slow cooling in a temperature region of 1150 ° C. or higher is indispensable for the simultaneous improvement of the relative dielectric constant and the Qf product aimed by the present invention. In particular, during cooling, it has been found that the effect is great under the condition that the slow cooling rate is slow in a temperature range of 1225 ° C. or higher and 1300 ° C. or lower. Then, it becomes possible to improve the Qf product efficiently. This minimizes an increase in manufacturing cost due to an extended cooling time.

The main component raw material powder is blended as shown in Table 1 in the ratio of xZrO ₂ .ySnO ₂ .zTiO ₂ (x, y, z is mol%, 31 ≦ x ≦ 42, 9 ≦ y ≦ 18, the balance is TiO ₂ ). In addition, La ₂ O ₃ , NiO, and Ta ₂ O ₅ are respectively u, v, w, and wt% (0 ≦ u ≦ 0.5, 0 ≦ v ≦ 0.5, 0 ≦ with respect to the total weight of the main components). w ≦ 0.5) The additives were blended as shown in Table 1, and after wet mixing, dehydration was performed, followed by calcination at 1100 ° C. for 4 hours in the air, followed by pulverization and granulation. Then, this powder was pressure-molded into a disk shape having a diameter of 14 mm and a height of 5.6 mm at a pressure of 1000 kg / cm ² , and sintered at 1375 ° C. in an air atmosphere after debinding. At the time of cooling after sintering, constant speed cooling was performed from 1375 ° C. to 1200 ° C. at a rate of 100 ° C./hour, and constant speed cooling was performed at a rate of 300 ° C./hour. Both surfaces of the obtained sintered body are polished, and using a cavity resonator method, a relative dielectric constant at a resonance frequency of 5 GHz, a Qf product, and a temperature coefficient τf of a resonance frequency at 25 ° C. to 75 ° C. are obtained. .

Furthermore, the sintered density of this sintered body was measured by the Archimedes method. Each sample within the scope of the present invention has a high sintered density and a density reaching the theoretical density of 96% or more, and not only can the desired electrical characteristics be stably obtained, but also a dense It was found that a sintered body was obtained. On the other hand, the composition no. 11, no. When the added amount of NiO and La ₂ O ₃ is out of the range of the present invention as in No. 12, even if the sintering temperature is 1350 ° C., the sintering density is 90% or less of the theoretical value and does not become dense. .

The main component raw material powder is blended as shown in Table 2 in the ratio of xZrO ₂ .ySnO ₂ .zTiO ₂ (x, y, z is mol%, 31 ≦ x ≦ 42, 9 ≦ y ≦ 18, the balance is TiO ₂ ). Furthermore, 0.2, 0.2, and 0.3 wt% of La ₂ O ₃ , NiO, and Ta ₂ O ₅ additives are blended with respect to the total weight of the main components, respectively, wet mixed, and then dehydrated. After calcination at 1100 ° C. for 4 hours in the air, pulverization and granulation were performed.

Thereafter, this powder was pressure-molded at a pressure of 1000 kg / cm ² so as to form a disk having a diameter of 23 mm and a height of 23 mm, and after debinding, it was sintered at 1375 ° C. At the time of cooling after sintering, constant speed cooling was performed from 1375 ° C. to 1200 ° C. at a rate of 100 ° C./hour, and constant speed cooling was performed at a rate of 300 ° C./hour. The ambient oxygen concentration during sintering and cooling is 21%, 30%, 60%, or 100%. A measurement sample having a diameter of 20 mm and a height of 8 mm is cut out from the center in the height direction of the obtained cylindrical sintered body having a diameter of about 20 mm and a height of about 20 mm, and a resonance frequency of 2 is measured using the cavity resonator method. The relative dielectric constant and Qf product at .8 GHz were obtained. The results are shown in Table 2.

  According to Table 2, when the oxygen concentration in the sintering atmosphere is 30% or more, the relative permittivity and the Qf product in all samples are compared with the case where the oxygen concentration in the sintering atmosphere is 21% (in the air). It can be seen that is improved.

The main component raw material powder is blended as shown in Table 3 in the ratio of xZrO ₂ .ySnO ₂ .zTiO ₂ (x, y, z is mol%, 31 ≦ x ≦ 42, 9 ≦ y ≦ 18, the balance is TiO ₂ ). Further, 0.2, 0.2, and 0.3 wt% of La ₂ O ₃ , NiO, and Ta ₂ O ₅ additives are blended with respect to the total weight of the main components, and after wet mixing, 1100 ° C. in the atmosphere. After calcination for 4 hours, pulverization and granulation were performed.

Thereafter, this powder was pressure-molded at a pressure of 1000 kg / cm ² so as to form a disk with a diameter of 23 mm and a height of 23 mm, and after debinding, it was sintered at 1375 ° C. with an oxygen concentration in the sintering atmosphere of 100%. Yui was done. During cooling after sintering, from 1375 ° C to 1300 ° C, from 1300 ° C to 1225 ° C, from 1225 ° C to 1150 ° C, from 1150 ° C to 1075 ° C, from 1075 ° C to 1000 ° C, etc. at 25 ° C / hour, etc. Rapid cooling was performed, and constant temperature cooling was performed at other temperature ranges at 300 ° C./hour.

  A measurement sample having a diameter of 20 mm and a height of 8 mm is cut out from the center in the height direction of the obtained cylindrical sintered body having a diameter of about 20 mm and a height of about 20 mm, and a resonance frequency of 2 is measured using the cavity resonator method. The relative dielectric constant and Qf product at .8 GHz are obtained and shown in Table 3. The relative dielectric constants of these samples did not depend on the temperature range of slow cooling, and were distributed within the range of 36.8 to 43.9.

  According to Table 3, when the temperature range for performing slow cooling is 1150 ° C or higher, the Qf product is distributed between 22 to 49 THz, and when the temperature range for performing slow cooling is 1150 ° C or lower, The Qf product is distributed in the range of 6 to 26 THz, and the Qf product is remarkably improved by setting the temperature range for performing slow cooling to 1150 ° C. or higher. Further, preferably, the temperature range of slow cooling is in the range of 1300 ° C. to 1225 ° C., and the Qf product is in the range of 37 to 49, indicating the highest value.

The main component raw material powder is blended in a weight ratio of xZrO ₂ .ySnO ₂ .zTiO ₂ (x, y, z is mol%, x = 33.5, y = 16, z = 50.5), Addition of 0.2, 0.2, and 0.3 wt% of La ₂ O ₃ , NiO, and Ta ₂ O ₅ additives to the weight, followed by calcining in air at 1100 ° C. for 4 hours And then pulverized and granulated. Thereafter, this powder was pressure-molded at a pressure of 1000 kg / cm ² so as to form a disk having a diameter of 23 mm and a height of 23 mm, and a binder removal treatment was performed.

  The oxygen concentration in the sintering atmosphere was as shown in Table 4, and sintering was performed at 1375 ° C. During cooling after sintering, cooling is performed at a constant temperature in the temperature range of 1300 ° C to 1150 ° C at 300 ° C / hour, 20 ° C / hour, 100 ° C / hour, 50 ° C / hour, 25 ° C / hour, and other temperatures. The cooling was performed at a constant rate of 300 ° C./hour. A measurement sample having a diameter of 20 mm and a height of 8 mm is cut out from the central portion in the height direction of the obtained cylindrical sintered body having a diameter of about 20 mm and a height of about 20 mm, and a resonance frequency of 2. mm is obtained using the cavity resonator method. The relative dielectric constant and Qf product at 8 GHz were determined, and the results are shown in Table 4.

  According to Table 4, it can be seen that in all the samples, the relative permittivity increases as the oxygen concentration in the sintering atmosphere increases. This increase was not dependent on the cooling rate. Further, when the cooling rate is 100 ° C./hour or less, the Qf product is distributed in the range of 32 to 43 THz, and when the cooling rate is larger than 100 ° C./hour, the Qf product is in the range of 21 to 30. The Qf product is remarkably improved by setting the cooling rate to 100 ° C./hour or less. That is, by setting the oxygen concentration during sintering / cooling to 30% or more and the cooling rate to 100 ° C./hour or less, both the relative dielectric constant and the Qf product are compared with those in the case of sintering in air. Can be improved at the same time.

Claims (4)

A dielectric ceramic composition comprising ZrO ₂ , SnO ₂ , TiO ₂ as main components and a main component composition ratio of xZrO ₂ .ySnO ₂ .zTiO ₂ (x + y + z = 100 mol%), wherein the composition ratio is 31 ≦ x ≦ 42, 9 ≦ y ≦ 18, the balance is TiO ₂ , and the addition amount of La ₂ O ₃ , NiO, Ta ₂ O ₅ with respect to the total weight of the main components is expressed as u, v, w, wt%, respectively. 0.1 ≦ u ≦ 0.5, 0.1 ≦ v ≦ 0.5, 0.1 ≦ w ≦ 0.5.   The dielectric ceramic composition according to claim 1, wherein the volume after sintering is 20 mm or more in diameter and 20 mm or more in height when converted to a hollow cylindrical shape, and the sintering temperature is 1300 ° C to 1450 ° C. In the range, the sintered atmosphere is sintered at an oxygen concentration of 30% or more, and is cooled at a temperature of 1150 ° C. or more at the time of cooling at a cooling rate corresponding to 100 ° C./hour or less when converted to constant cooling or multistage cooling or Produced by holding at a constant temperature, the dielectric constant is 36 to 44, the Q · f product is 20 THz or more, and the absolute value of the temperature coefficient τf of the resonance frequency at 25 to 75 ° C. is 35 ppm / ° C. or less. A dielectric ceramic composition characterized by the above. A method for producing a dielectric ceramic composition mainly composed of ZrO ₂ , SnO ₂ , and TiO ₂ , wherein the composition ratio is expressed as xZrO ₂ .ySnO ₂ .zTiO ₂ (x + y + z = 100 mol%). The ratio is 31 ≦ x ≦ 42, 9 ≦ y ≦ 18, the balance is TiO ₂ , and the addition amounts of La ₂ O ₃ , NiO, Ta ₂ O ₅ with respect to the total weight of the main components are u, v, w, wt, respectively. %, 0.1 ≦ u ≦ 0.5, 0.1 ≦ v ≦ 0.5, 0.1 ≦ w ≦ 0.5, and the raw material of the dielectric ceramic composition has an oxygen concentration of 30%. A method for producing a dielectric ceramic composition, comprising sintering in a temperature range of 1300 ° C. to 1450 ° C. in the above sintering atmosphere.   4. The method for producing a dielectric ceramic composition according to claim 3, wherein the sintering is performed at an oxygen concentration of 30% or higher and at a temperature of 1150 [deg.] C. or higher when the sintering is performed and cooling is subsequently performed. A method for producing a dielectric ceramic composition comprising performing slow cooling, multistage cooling, or constant temperature holding at a cooling rate corresponding to 100 ° C./hour or less in terms of cooling.