DE2750203A1 - LOW-LOSS CERAMIC COMPOSITION AND METHOD OF MANUFACTURING IT - Google Patents

Description

Matsushita Electric Industrial Co., Ltd., 1006, Oaza Kadoma, Kadoma-shi, Osaka-fu (Japan)

Low-loss ceramic composition and method for its manufacture

The invention is concerned with a ceramic mass used in electrical and electronic equipment can be, especially with a ceramic mass that has a high dielectric constant, low loss for electromagnetic radiation in the microwave range and is insensitive to temperature fluctuations, so that the mass is used with particular advantage in various high frequency circuits can be.

In the microwave range, dielectrics are used for impedance matching in high-frequency circuits and as dielectric Resonators, etc. used. In the development of integration technology in the field of microwave circuits there is a strong need for small dielectric resonators as stabilizers for the oscillator frequency, as a frequency filter, etc., as well as on substances with

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high dielectric constant and low loss for microwaves, which can cope with the temperature fluctuations that occur are sufficiently stable and consequently, for example, as substrates or chips for integrated Circuits can be used.

Although alumina is a low loss dielectric and can be used as a substrate, it has disadvantages in that its relative dielectric constant is small, about 10, and has a large temperature coefficient is from about 120 to 150 ppm / ° C.

Various compositions can be used for dielectric resonators, for example compositions of the BaO-TiO ₂ group, compositions obtained by substituting other elements for part of the BaO-TiO ₂ "group, or compositions obtained by combining TiO-, its Dielectric constant has a negative temperature gradient, with compositions whose dielectric constant has a positive temperature coefficient. However, these compositions have disadvantages, which can be seen in a large dielectric loss, large temperature fluctuations with respect to the dielectric constant, large deviations in the temperature profile of the dielectric constant, etc., so that there are numerous problems in practical use.

The invention is therefore based on the object of dielectric ceramic compositions for use in electrical and to create electronic devices that have a large dielectric constant and that are suitable for microwaves form only a small loss and also have sufficient stability against temperature fluctuations. The too Creating compositions are said to have a simple structure

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"*" "27502Ü3

and have a stable operation and be inexpensive to manufacture on a large scale. The invention is about also develop a method for making these dielectric ceramic compositions.

For this purpose, the invention proposes a fired composition which contains more than two types of the following components: 3BaO-ZnO'Nb-O ₅ , 3BaO-ZnO-Ta ₃ O ₅ , 3BaO'MgO-Nb ₃ O ₅ and 3BaO-MgO-Ta ₃ O ₅ ; these compositions are prepared under optimal conditions as described below and used as ceramic masses which have a very low microwave loss and a large dielectric constant and can be used for use as dielectric resonators, electrical filters, substrates, etc., with the above-mentioned disadvantages of the substances mentioned there no longer occur, and the production process for the compositions according to the invention is very inexpensive.

The invention is based on the following description in which an exemplary embodiment is shown with reference to the accompanying drawing. The figure shows an electrical block diagram of a circuit used to measure the dielectric properties of ceramic Substances in the microwave range is suitable.

Through numerous experiments it was found that compositions formed from a correct connection of BaO, ZnO, MgO, Nb ₃ O ₅ and T ^ ⁰ S and fired into dense ceramic bodies, a high unloaded Q-value and good stability with respect to temperature variations in the microwave frequency range. By properly changing the compositions, dielectric ceramic compositions for use in the microwave frequency range can be obtained which have superior properties to the relative

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Have dielectric constants from 29 to 39, Q values from 3,900 to 4,300, and a temperature coefficient of resonance frequency from zero to 27 ppm / ° C. A structural analysis was carried out for the components 3BaO-ZnO-Nb ₂ O ₅ , 3BaO-MgO-Nb ₃ O ₅ , 3BaO-ZnO-Ta-O ₅ and 3BaO-MgO-Ta ₂ O ₅ , for example in (1) F. Glasso et al., Nature, 207, 70 (1965); (2) F. Glasso et al., Inorg. Chem., 2, 3, 482 (1963); (3) F. Glasso et al. J. Phys. Chem., 67, 1561 (1963), and (4) F. Glasso et al. J. Am Chem., Soc, 81, 820 (1959), so that reference can be made to these publications for further details. Furthermore, single crystals of these components were prepared for examination of their electrical properties; because of the very small size of such single crystals, it has been very difficult to put them into practical use.

To overcome the disadvantages mentioned, dense ceramic masses of the BaO-ZnO-MgO-Nb-Oc-Ta-Oc group were prepared to measure their electrical properties in the microwave frequency range. As a result, it was found that the composition represented by the formula w (3BaO-ZnO «Nb ₂ O ₅ ) - X (SBaO-ZnO-Ta ₃ O ₅ ) - y (3BaO-MgO-Nb ₂ O ₅ ) - ζ (3BaO ^ MgO-Ta ₂ O ₅ ) has a high unloaded Q value in the microwave frequency range and high temperature stability for the resonance frequency when used as a dielectric resonator.

Table I shows the relative dielectric constants K, the unloaded p-values and the temperature coefficients the resonance frequency TCF of dielectric resonators from the ceramic compositions according to the invention in the microwave frequency range .

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experiment
Nos. Composition
(Mole fraction) χ U ζ ilut-l'rcss inji
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( ⁰ C) K Q TCF
(ppm / ° C) W. 1,300 40 3.485 28 * 1 1.0 1.0 1,400 30th 3,666 - 2 * 2 1.0 1,200 29 3,800 24 * 3 1.0 1,450 27 3,780 9 * 4 0.99 1,380 31 3,972 0 5 0.01 0.6 1,350 33 4,319 9 6th 0.4 0.4 1,350 35 3,938 17th 7th 0.6 0.01 1,300 39 3.917 25th 8th 0.99 0.99 1,200 31 4.111 24 9 0.01 0.6 1,250 34 4,237 25th 10 0.4 0.4 1,250 35 4.150 24 11 0.6 0.01 1,300 38 4.020 27 12th 0.99 0.01 0.99 1.430 28 4.033 7th 13th 0.4 0.6 1.420 28 4,270 5 14th 0.6 0.4 1.420 29 4.214 4th 15th 0.99 0.01 1,400 30th 3,950 0 16 0.01 0.99 1.430 27 4.04 7 11 17th 0.4 0.6 1,400 28 4.253 15th 18th 0.6 0.4 1,350 29 4.221 19th 19th 0.99 0.01 1,200 29 4.125 22nd 20th 0.01 0.01 0.01 1.330 29 4,228 11 21 0.97 0.97 0.01 0.0] 1,370 30th 4.257 20th 22nd 0.01 0.01 0.97 0.0 1,300 31 4.125 5 23 0.01 ί 0.0] L 0.01 0.9 1 1,400 37 4.0.17 23 24 0.0] > 0.2! ) 0.25 0.2 S 1.380 34 4.111 12th 25th 0.2!

* For comparison

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Table 2 shows changes in the unloaded Q value under the conditions of the manufacturing process according to the invention for the ceramic bodies.

Table 2

Composition
(Mole Fraction) X y Z llot pressing
temperature Q 1,000 1,400 1,450 W. 0.99 1,380 Calcining
Firing temperature (° ( 3,970 3,950 2.210 0.01 0.5 1,350 800 4.015 4,000 2.234 0.5 0.1 1,300 590 3,910 3.890 2.180 0.99 0.99 1,200 500 4.102 3,920 1.290 0.01 0.5 1,250 485 3.903 3,915 1,310 0.5 0.01 1,300 920 4.015 3,900 1,250 0.99 0.01 0.99 1.430 890 4.028 3,970 926 0.5 0.5 1.420 905 3,940 4.115 950 0.99 0.01 1,400 1.530 3.935 3,860 890 0.01 0.99 1.430 1.523 4.038 4.010 1.680 0.5 0.5 1,350 1.510 3,990 4.022 1.707 0.99 0.01 1,200 1.225 4.110 4.050 1.715 0.25 0.25 0.25 1,380 1.219 4.150 4.110 2,321 0.25 1.180 1.111

* For comparison

The block diagram shown in the accompanying drawing shows a circuit for measuring the dielectric properties of ceramic masses in the microwave range. The measuring method is described in detail, for example, in B.W. Hakki i.a., IRE Trans. MTM-14, 9, 400 (1966), described, with which the dielectric constant, the loss, the temperature stability etc. of the dielectric ceramics im

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Microwave range can be measured exactly. On the basis of the method described, measurements were carried out on cylindrical samples, each of which had a diameter of 5 to 6 mm and a thickness of 2 to 2.5 mm. The measurement frequency was about 11.5 GHz. The dielectric constant was determined from the sample size and the resonance frequency. In addition, the temperature coefficient for the resonant frequency from a variation of the resonance frequency at temperatures between -20 ⁰ C and 100 ⁰ C was obtained. The TCF can be represented by the following equation by using the temperature coefficient of dielectric constant TCK and the coefficient of thermal expansion CC _- / as follows:

TCF = - (TCK / 2

The TCF value is used as a property to describe the temperature stability in microwave circuits The substances to be used are particularly helpful. For example, if the dielectric resonator is made by using the ceramic masses explained above is built up, the stability of the resonance frequency is determined by the value TCF while the loss by 1/0 results from the unloaded Q-value, with a larger Q-value leading to a leads to less loss.

The composition of the dielectric material according to the invention can be represented in closed form by the formula 3BaO-M ¹ O-MjO ₅ , where M ^{1 is} zinc or magnesium and M "is then niobium or tantalum. It should be noted that the ceramic materials according to the invention are a solid solution containing at least more than two of M ¹ or M "from the compositions mentioned.

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The compositions of the present invention can be obtained by mixing the starting material with oxides, carbonates and hydroxides each containing barium, zinc, magnesium, niobium and tantalum to give a predetermined composition. The resulting mixture is then calcined or fired for more than 30 minutes at temperatures between 1000 and 1400 ⁰ C, then ground matt and dried, and then hot pressing and firing at temperatures of 1200 ⁰ C to 1450 ⁰ C for at least 30 minutes under a Subjected to pressure greater than 50 kg / cm ² . If the temperature in this manufacturing process for firing ^{exceeds 14 00 0} C, there is a risk that the electrical properties of the resulting ceramic masses are deteriorated or destroyed due to the increasing evaporation of BAO and ZnO in the mass, while on the other hand, the increase in Hot-pressing temperature above 1450 ^° C. is undesirable because cracks may occur in the resulting ceramic products or in the molds for hot-pressing. The time for firing and hot-pressing should not drop below 30 minutes in order to avoid an undesirable increase in deviations in the properties of the end products. For example, at hot- ^{pressing temperatures below 1200 °} C. and pressures below 50 kg / cm ^2, ceramic masses of good quality cannot be obtained because the firing is insufficient, while firing temperatures below 1000 ^° C. and over 1400 ^° C. lead to a poorer quality. Value can lead.

The dielectric ceramic produced according to the invention Materials have a large dielectric constant, low loss against microwaves and good stability against Temperature fluctuations when treated according to the conditions set out in the appended claims.

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The following examples illustrate the invention in a non-limiting manner. The influence of the firing temperature is illustrated in Example II with reference to Table II above.

EXAMPLE I

The raw materials mixed to form a predetermined composition were wet mixed using distilled water. The resulting mixture was fired for two hours at a temperature of 1100 ^° C. and then finely ground and dried, and then molded ^{under a pressure of 700 kg / cm 2.} The molded material was then subjected to hot press baking under a pressure of 200 kg / cm ^{3 for} two hours using a mold made of silicon carbide (SiC). The compositions and the hot-press temperature are listed in Table I. As can be seen from Table I, the ceramic materials obtained according to the invention have a dielectric constant between 27 and 40, unloaded Q values above 3900 and stability to temperature fluctuations between 0 ppm / ° C. and 28 ppm / ° C., which is sufficiently small.

By correctly selecting the compositions, ceramic masses that have a large unloaded Q value on the microstrip of aluminum oxide substrates, for example those whose unloaded Q value is above 4000, can be produced according to the method according to the invention, for example according to experiment number 6 in table I, where the stability TCF to temperature fluctuations is at any value between ο ppm / ⁰ C and 28 ppm / ⁰ C as desired.

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EXAMPLE II

In Example II, only the firing temperature was changed and the other processing conditions were exactly the same as described in Example I above. The unloaded Q values in Example II are shown in Table 2. It can be seen from this that at firing temperatures below 900 ^° C. or above 1400 ^° C. the unloaded Q values are extremely reduced, so that the resulting ceramic products cannot be used as dielectrics in microwave circuits.

From the above description it should be clear that according to the invention dielectric ceramic materials or compositions with low microwave loss and high dielectric constant are prepared from fired material which contains compositions which contain more than two types of the components 3BaO 'ZnO-Nb ₃ O ₅ , 3BaO ^- ZnO-Ta ₂ O ₅ , 3BaO-MgO-Nb ₃ O ₅ and 3BaO-MgO-Ta ₃ O ₅ , and which can be produced by the above-described process according to the invention. These ceramic materials or compositions can be used as dielectric resonators, electrical filters, substrates, etc. and do not have the disadvantages explained at the beginning. The invention is of course not limited to the details shown.

Overall, a fired material has been described which contains compositions containing more than two kinds of the components 3BaCZnO-Nb ₃ O ₅ , 3BaO-ZnO-Ta O ₅ , 3BaO-MgO-Nb ₃ O ₅ and 3BaO-MgO-Ta ₃ O ₅ The material is produced under optimal processing conditions as described and is used to obtain ceramic masses which have a low microwave loss and high dielectric constant and which can be used as dielectric resonators, electrical filters, substrates, etc.

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Number: 27 50203 Int. Cl. *: C 04 B 35/00 Registration date: November 10, 1977 Disclosure date: 17th May 1979

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Claims (6)

-JH- claims 1. Ceramic composition with low power dissipation in the microwave range, which essentially consists of a solid solution with the formula: w (3BaO-ZnO-Nb ₂ O ₅ ) -x (3BaO-ZnO-Ta ₃ O ₅ ) where w and χ mean the mole fraction and satisfy the relations 0.015 w < 0.99, 0.01 <χ <0.99 and w + χ = 1. 2. Ceramic composition with low power dissipation in the microwave range, consisting essentially from a solid solution with the formula w (3BaO-ZnO-Nb ₂ O ₅ ) -y (3BaO-MgO'Nb ₃ O ₅ ) where w and y represent the mole fraction and satisfy the relations 0.01 <w < 0.99, 0.01 <y < 0.99 and w + y = 1. 3. Ceramic composition with low power dissipation in the microwave range, consisting essentially from a solid solution with the formula χ (3BaO-ZnO-Ta ₂ O ₅ ) -zOBaO-MgO-Ta ₂ O ₅ ) where χ and ζ denote the mole fraction and satisfy the relations 0.01 i χ 1 0.99, 0.01 i ζ £ 0.99 and χ + ζ = 1. 909820/0041 ORIGINAL INSPECTBQ - yr - 4. Ceramic composition with low power loss in the microwave range, consisting essentially from a solid solution of the formula yOBaO-MgO-Nb ₂ O ₅ ) -z (3BaO-MgO-Ta ₂ O ₅ ) where y and ζ represent the mole fraction and the relations 0.01 ύ. γ ύ 0.99, 0.01 4 ζ ύ 0.99 and y + ζ = 1 are sufficient. 5. Ceramic composition with low power loss in the microwave range, consisting essentially from a solid solution of the formula w (3BaO · ZnO · Nb ₂ O ₅ ) -x (3BaO-ZnO-Ta ₂ O ₅ ) -y (3BaO-MgO-Nb ₃ O ₅ ) -z (3BaO-MgO-Ta ₂ O ₅ ) where w, x, y and ζ represent the mole fractions and the relations 0.01 <w <0.97, 0.01 <χ < 0.97, 0.01 ^ y ^ 0.97 and 0.01 ^ ζ ^ 0.97 and w + x + y + z = 1 are sufficient. 6. A method for producing a ceramic composition with low power loss in the microwave range according to one or more of the preceding claims, characterized in that a solid solution-forming mixture of the oxides, and / or hydroxides, and / or carbonates in the ceramic compositions contained metals is ^{fired at 1000 0} C to 1400 ⁰ C for at least 30 minutes and then hot-pressed at a pressure of at least 50 kg / cm ² and a temperature of 1100 ⁰ C to 1450 ⁰ C for at least 30 minutes. 909820/0041