Dielectric ceramic composition

Abstract: A dielectric ceramic composition mainly comprises a major component which comprises barium, titanium, neodymium, samarium and oxygen and is represented by the following compositional formula: xBaO-yTiO₂-zNd₂O₃-tSm₂O₃ (wherein 0.1≦x≦0.2; 0.5≦y≦0.8; 0.01≦z≦0.2; 0≦t≦0.2, provided that x+y+z+t = 1 ); and a minor component mainly comprising glass powder having a softening point of about 100 to about 500°C, which mainly comprises PbO, ZnO and B₂O₃, and GeO₂, and wherein the content (a) (% by weight) of the glass powder falls within the range of 1≦a≦25 and the content (b) (% by weight) of GeO₂ falls within the range of 0.5≦b≦10, on the basis of the weight of the major component. The major component may further comprise Bi₂O₃ and the composition may comprise bismuth as a minor component. The dielectric ceramic composition can be sintered at a low temperature and exhibits excellent characteristic properties such that it has a large specific dielectric constant ε r , a large unloaded Q and a small temperature coefficient of the resonance frequency.

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to a dielectric ceramic composition suitably used as a material for a dielectric resonator or the like. Disclosure of the Prior Art: There has recently been desired for the development of a small-sized and high performance dielectric resonator as integration of microwave circuits is increased. The dielectric ceramic composition used in such dielectric resonators must satisfy various requirements. For instance, the composition should have a large specific dielectric constant ε r , a large unloaded Q and a low temperature coefficient of resonance frequency τ f . As examples of such dielectric ceramic compositions, Ber. Dt. Keram. Ges., 55 (1978), Nr. 7 and JPA No. Sho 60-35406 propose dielectric ceramic compositions comprising BaO-TiO 2 -Nd 2 O 3 systems. Moreover, U.S. Patent No. 5,292,694 discloses a dielectric ceramic composition comprising a BaO-TiO 2 -RE 2 O 3 system (wherein "RE" represents a rare earth metal). In addition, JPA No. Sho 62-72558 discloses a dielectric ceramic composition comprising a BaO-TiO 2 -Nd 2 O 3 -Bi 2 O 3 system. There have recently been developed a laminated chip condenser and a laminated dielectric resonator, which are prepared by laminating a dielectric ceramic composition. In this respect, the ceramic composition and the internal electrode have been laminated by simultaneous firing. However, it is difficult to simultaneously firing the foregoing dielectric ceramic composition and the internal electrode, since the firing temperature of the former is high of the order of 1300 to 1400 °C and therefore, electrode materials for producing laminated structures are limited to those which are proof against a high temperature such as palladium (Pd) and platinum (Pt). For this reason, there has long been desired for the development of a dielectric ceramic composition capable of being fired simultaneously with cheaper electrode materials such as silver (Ag), silver-palladium (Ag-Pd) and copper (Cu), at a low temperature of not higher than 1200°C. SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a dielectric ceramic composition which has excellent properties as a material for dielectric resonators or the like, in particular, a high dielectric constant, a high unloaded Q and low temperature-dependency of the resonance frequency and which exhibits good sinterability even if it is fired at a low temperature. According to an aspect of the present invention, there is provided a dielectric ceramic composition which mainly comprises a major component comprising barium, titanium, neodymium, samarium and oxygen and represented by the following compositional formula: xBaO-yTiO 2 -zNd 2 O 3 -tSm 2 O 3 (wherein 0.1≦x≦0.2; 0.5≦y≦0.8; 0.01≦z≦0.2; 0≦t≦0.2, provided that x+y+z+t = 1 ); and a minor component mainly comprising glass powder, which mainly comprises PbO, ZnO and B 2 O 3 , and GeO 2 , and wherein the content (a) (% by weight) of the glass powder falls within the range of 1≦a≦25 and the content (b) (% by weight) of GeO 2 falls within the range of 0.5≦b≦10, on the basis of the weight of the major component. According to another aspect of the present invention, there is provided a dielectric ceramic composition mainly comprising a major component which comprises barium, titanium, neodymium, samarium, bismuth and oxygen and is represented by the following compositional formula: xBaO-yTiO 2 -zNd 2 O 3 -tSm 2 O 3 -wBi 2 O 3 (wherein 0.1≦x≦0.2; 0.5≦y≦0.8; 0.01≦z≦0.2; 0.01 ≦t≦0.2; 0.005≦w≦0.05, provided that x+y+z+t+w = 1 ); and a minor component mainly comprising glass powder, which mainly comprises PbO, ZnO and B 2 O 3 , and GeO 2 , and wherein the content (a) (% by weight) of the glass powder falls within the range of 1≦a≦25 and the content (b) (% by weight) of GeO 2 falls within the range of 0.5≦b≦10, on the basis of the weight of the major component. The dielectric ceramic composition of the present invention may further comprise Li 2 O as a minor component and the content (c) (% by weights of Li 2 O falls within the range of 0.04≦c≦4 on the basis of the weight of the major component. The dielectric ceramic composition may also contain Nb 2 O 5 , MnO, Al 2 O 3 and/or ZnO. In the ceramic composition of this invention, the content of PbO, ZnO and B 2 O 3 in the glass powder are preferably in the range of 5≦PbO≦90 5≦B 2 O 3 ≦60 and 0<ZnO≦65, more preferably 0<ZnO≦50 (% by weight). If the softening point of the glass powder is higher than about 500°C, it becomes difficult to fire at a low temperature. Although there is no limitation on the lower limit of the softening point of the glass powder, it is usually about 100°C. It has been found that the dielectric ceramic composition of this invention has excellent characteristic properties such that it can be sintered at a low temperature and that it has a high dielectric constant, a large unloaded Q and low temperature-dependency of the resonance frequency. The present invention also provides a dielectric device such as a dielectric resonator and a dielectric filter, comprising the dielectric ceramic composition as above. DETAILED DESCRIPTION OF THE INVENTION First, the relative amounts of the oxides constituting the major component of the dielectric ceramic composition according to the present invention will be explained below. If the molar fraction of BaO exceeds the foregoing upper limit, the dielectric resonator produced from the resulting dielectric ceramic composition does not undergo any resonance. On the other hand, if it is less than the lower limit, the resulting dielectric resonator exhibits a low dielectric constant and a low unloaded Q. If the molar fraction of TiO 2 is greater than the upper limit defined above, the resulting dielectric resonator shows a large temperature coefficient of the resonance frequency, while if it is less than the lower limit, the dielectric constant of the resulting resonator is low. Moreover, if the molar fraction of Nd 2 O 3 is greater than the upper limit defined above, the resulting dielectric resonator exhibits a low dielectric constant and a low unloaded Q, while if it is less than the lower limit, the temperature coefficient of the resonance frequency observed for the resulting dielectric resonator has a tendency to increase. In addition, the molar fraction of Sm 2 O 3 has an effect on the dielectric constant, the unloaded Q and the temperature coefficient of the resonance frequency of the resulting dielectric resonator and therefore, a dielectric resonator exhibiting the desired characteristic properties can be produced only when it falls within the range defined above. In the present invention, if the content of the minor component relative to the major component, i.e., the content (a) (% by weight) of the glass powder which mainly comprises PbO, ZnO and B 2 O 3 and the content (b) (% by weight) of GeO 2 are extremely high, the unloaded Q of the resulting dielectric resonator is reduced, while these contents (a) and (b) are too low or zero, it becomes difficult to fire the resulting composition at a low temperature of not higher than 1200 °C. For this reason, the content of the minor component relative to the major component, i.e., the content (a) (% by weight) of the glass powder which mainly comprises PbO, ZnO and B 2 O 3 and the content (b) (% by weight) of GeO 2 are limited to the foregoing ranges, respectively. Moreover, the relative proportions of PbO, ZnO and B 2 O 3 which constitute the glass powder are not particularly restricted, but if the content of ZnO is too high, the softening point of the resulting glass increases and it is difficult to fire the resulting composition at a low temperature. Accordingly, the content of ZnO in the glass powder is preferably 0<ZnO≦65, more preferably 0<ZnO≦50. The content of PbO and B 2 O 3 falls preferably within 5≦PbO≦90 and 5≦B 2 O 3 ≦60 (% by weight), respectively. And, if the softening point of the minor comonent, glass powder, is higher than about 500°C, it becomes difficult to fire at a low temperature. The dielectric ceramic composition of the present invention may further comprise, as a minor component, Li 2 O such that the content (c) (% by weight) thereof falls within the range of 0.04≦c≦4. The addition of Li 2 O permits a further decrease of the sintering temperature of the composition and as a result, an internal electrode of Ag can easily be formed. If the content (c) of Li 2 O exceeds the upper limit defined above, the dielectric resonator produced from the resulting dielectric ceramic composition never undergoes resonance. According to a second aspect of the present invention, there is further provided a dielectric ceramic composition which mainly comprises a major component comprising barium, titanium, neodymium, samarium, bismuth and oxygen and represented by the following compositional formula: xBaO-yTiO 2 -zNd 2 O 3 -tSm 2 O 3 -wBi 2 O 3 (wherein 0.1≦x≦0.2; 0.5≦y≦0.8; 0.01≦z≦0.2; 0.01≦t≦0.2; 0.005≦w≦0.05, provided that x+y+z+t+w = 1 ); and a minor component mainly comprising glass powder, which mainly comprises PbO, ZnO and B 2 O 3 , and GeO 2 , and wherein the content (a) (% by weight) of the glass powder falls within the range of 1≦a≦25 and the content (b) (% by weight) of GeO 2 falls within the range of 0.5≦b≦10, on the basis of the weight of the major component. If the softening point of the minor component, glass powder is higher than about 500°C, it becomes difficult to fire at a low temperature. In this composition, if the molar fraction of Bi 2 O 3 is excessively high, the resulting composition exhibits a low dielectric constant and a low unloaded Q, while if it is extremely low, the dielectric resonator produced from the resulting composition has a high temperature coefficient of the resonance frequency. In the foregoing formula (2), the proportions of x, y, z and t as well as the contents (a) and (b) of the glass powder and GeO 2 as the minor component are limited to the foregoing ranges respectively, for the same reasons discussed above in connection with the foregoing formula (1). This dielectric ceramic composition has excellent characteristic properties like the foregoing composition according to the first aspect such that it can also be sintered at a low temperature and that it has a high dielectric constant, a large unloaded Q and low temperature-dependency of the resonance frequency. The dielectric ceramic composition according to the second aspect of the present invention may further comprise, as a minor component, Li 2 O such that the content (c) (% by weight) thereof falls within the range of 0.04≦c≦4. In this case, the addition of Li 2 O likewise permits a further decrease of the sintering temperature of the composition and as a result, an internal electrode of Ag can easily be formed. If the content (c) of Li 2 O exceeds the upper limit defined above, the dielectric resonator produced from the resulting dielectric ceramic composition never undergoes resonance. In the present invention (the first and second aspects), at least one member selected from the group consisting of Nb 2 O 5 , MnO, Al 2 O 3 and ZnO may be added to the composition as the third component and this permits a further reduction in the absolute value of the temperature coefficient τ f of the resonance frequency. If the content d (% by weight) of the third component on the basis of the major component is extremely high, the temperature coefficient τ f of the resonance frequency increases. Therefore, the content (d) thereof falls within the range of 0≦d≦2, preferably 0.1≦d≦2. Then a preferred method for preparing the dielectric ceramic composition of the present invention will be described below. A starting material comprising various oxides constituting the major component, for instance, barium carbonate, titanium oxide, neodymium oxide, samarium oxide and, if necessary, bismuth oxide is subjected to wet blending in predetermined portions together with a solvent such as water or an alcohol. Subsequently, the solvent such as the water or the alcohol was removed, followed by pulverization of the mixture and then calcination thereof at a temperature ranging from 1000 to 1300 °C for about 1 to 5 hours in an oxygen-containing gas atmosphere (for instance, in the air). The calcined powder thus prepared is wet-blended with the minor component, i.e., the glass powder which is composed of PbO, ZnO and B 2 O 3 and GeO 2 , and if necessary, Li 2 O and the third component, i.e., at least one member selected from the group consisting of Nb 2 O 5 , MnO, Al 2 O 3 and ZnO in the presence of a solvent such as an alcohol. Then the solvent such as the water or the alcohol is removed and thereafter the mixture is pulverized. Moreover, the product is uniformly mixed with an organic binder such as polyvinyl alcohol, followed by drying, pulverization and pressure molding (under a pressure ranging from about 100 to 1000 kg/cm 2 ). Thereafter, a dielectric ceramic composition represented by the foregoing compositional formula (1) or (2) can be obtained by firing the resulting molded article at a temperature ranging from 850 to 1100 °C in an oxygen-containing gas atmosphere, for instance, in the air. The dielectric ceramic composition thus prepared may be, according to need, processed into appropriate shapes and sizes, or formed into a sheet by, for instance, the doctor blade technique followed by lamination of the sheet with an electrode and may thus be used as a material for a dielectric resonator, a dielectric substrate, a laminated element or the like. As raw materials for barium, titanium, neodymium, samarium, niobium, bismuth, lead, zinc, boron, germanium, manganese, aluminum and lithium, there may be used, for instance, nitrates and hydroxides thereof which are converted into oxides during the firing process in addition to oxides thereof such as BaCO 3 , TiO 2 , Nd 2 O 3 , Sm 2 O 3 , Bi 2 O 3 , PbO, ZnO, B 2 O 3 , GeO 2 , Nb 2 O 5 , MnO, Al 2 O 3 and LiO 2 The present invention will hereinafter be described in more detail with reference to the following non-limitative working Examples and Comparative Examples. Example 1 Barium carbonate powder (BaCO 3 ; 0.13 mole), titanium oxide powder (TiO 2 ; 0.70 mole) and neodymium oxide powder (Nd 2 O 3 ; 0.17 mole) were charged in a ball mill together with ethanol and then subjected to wet blending for 12 hours. After the removal of the solvent from the dispersion, the mixture was pulverized and then calcined at 1250 °C in the air. Separately, glass powder A comprising 84wt% of lead oxide powder (PbO), 7 wt% of zinc oxide powder (ZnO) and 9 wt% of boron oxide powder (B 2 O 3 ) was prepared according to the usual method. To the calcined product prepared above, there were added 2 wt% of the glass powder A comprising PbO, ZnO and B 2 O 3 , and 3 wt% of germanium oxide powder (GeO 2 ), followed by introduction of the mixture into a ball mill together with ethanol and then wet blending for 48 hours. After the removal of the solvent from the dispersion, the mixture was pulverized, followed by addition of an appropriate amount of a polyvinyl alcohol solution to the pulverized product, drying the mixture, forming it into pellets having a diameter of 12 mm and a thickness of 4 mm and then firing the pellets at 970°C for 2 hours in the air. The composition of the product and the sintering temperature thereof are summarized in the following Table 1. The ceramic composition thus prepared was processed into pieces each having a diameter of 7 mm and a thickness of about 3 mm and inspected for the specific dielectric constant ε r , the unloaded Q and the temperature coefficient τ f of the resonance frequency at a resonance frequency (ranging from 3 to 6 GHz) according to the dielectric resonance method. The results thus obtained are listed in the following Table 2. Examples 2 to 22 and Comparative Examples 1 to 12 The same procedures used in Example 1 were repeated except that the mixing ratio of barium carbonate, titanium oxide, neodymium oxide and samarium oxide; the kinds of glass powder comprising PbO, ZnO and B 2 O 3 (glass powder B: 80 wt% PbO, 10 wt% ZnO and 10 wt% B 2 O 3 ) and the added amounts of the minor components as well as the added amount (d) of the third component were changed as detailed in Table 1 to prepare dielectric ceramic compositions and they were inspected for characteristic properties. The compositions of the products prepared in these Examples and Comparative Examples and characteristic properties thereof are summarized in Table 2. COMPOSITION OF DIELECTRIC CERAMIC BaO x TiO 2 y Nd 2 O 3 z Sm 2 O 3 t GLASS POWDER wt% KIND OF GLASS GeO 2 wt% d wt% CALCINATION TEMPERATURE °C EXAMPLE 1 0.13 0.70 0.17 0 2 A 3 - 970 2 0.18 0.67 0.11 0.04 7 A 3 - 940 3 0.18 0.67 0.11 0.04 10 A 3 - 915 4 0.18 0.67 0.11 0.04 15 A 3 - 890 5 0.16 0.67 0.11 0.06 20 A 2 - 880 6 0.18 0.66 0.13 0.03 5 B 5 - 990 7 0.17 0.67 0.10 0.06 10 B 3 - 960 8 0.16 0.65 0.17 0.02 15 B 3 - 940 9 0.13 0.70 0.17 0 7 A 3 - 950 10 0.13 0.70 0.15 0.02 7 A 3 - 945 11 0.13 0.70 0.12 0.05 7 A 3 - 950 12 0.14 0.71 0.04 0.11 10 A 5 - 935 13 0.17 0.66 0.17 0 10 A 5 - 925 14 0.17 0.66 0.17 0 10 A 7 - 915 15 0.17 0.66 0.17 0 10 A 10 - 935 16 0.16 0.65 0.18 0.01 7 A 3 - 940 17 0.15 0.67 0.18 0 10 A 5 - 905 18 0.15 0.67 0.18 0 15 A 3 - 875 19 0.15 0.67 0.18 0 12 A 5 0.5(Nb 2 O 5 ) 910 20 0.15 0.67 0.18 0 12 A 5 0.5(MnO) 915 21 0.15 0.67 0.18 0 12 A 5 0.5(Al 2 O 3 ) 920 22 0.15 0.67 0.18 0 12 A 5 0.5(ZnO) 910 COMPARATIVE EXAMPLE 1 0.05 0.75 0.19 0.01 10 A 5 - 960 2 0.30 0.57 0.11 0.02 10 A 3 - 935 3 0.08 0.86 0.05 0.01 15 A 3 - 920 4 0.15 0.45 0.39 0.01 9 A 2 - 930 5 0.11 0.57 0.31 0.01 10 A 2 - 920 6 0.10 0.89 0 0.01 10 A 2 - 925 7 0.14 0.55 0.01 0.30 5 A 3 - 945 8 0.15 0.70 0.13 0.02 0 - 0 - 1420 9 0.16 0.67 0.11 0.06 30 A 2 - 870 10 0.16 0.65 0.17 0.02 30 B 3 - 860 11 0.17 0.66 0.17 0 20 A 0 - 1160 12 0.15 0.70 0.13 0.02 10 A 15 - 890 ELECTRIC CHARACTERISTICS ε r Q τ f ppm/°C EXAMPLE 1 71.0 1510 13 2 76.0 1190 6 3 70.0 1120 -5 4 68.0 910 -8 5 65.0 660 -22 6 74.0 1080 12 7 70.0 750 -7 8 67.0 615 -5 9 69.0 1305 8 10 69.5 1180 -7 11 68.0 975 21 12 61.0 715 -2 13 68.0 1060 18 14 64.0 1020 14 15 58.0 910 8 16 71.0 1120 16 17 62.0 1070 -46 18 66.0 720 -49 19 61.0 1100 -30 20 63.0 1120 -25 21 62.0 1090 -32 22 61.0 1110 -21 COMPARATIVE EXAMPLE 1 44.0 150 -1 2 NO RESONANCE 3 64.0 305 140 4 35.0 205 45 5 43.0 80 -6 6 60.0 1510 86 7 41.0 260 -31 8 87.0 2870 18 9 27.0 195 -7 10 23.0 145 7 11 94.0 80 81 12 41.0 220 -43 Example 23 Barium carbonate powder (BaCO 3 ; 0.13 mole), titanium oxide powder (TiO 2 ; 0.70 mole) and neodymium oxide powder (Nd 2 O 3 ; 0.17 mole) were charged in a ball mill together with ethanol and then subjected to wet blending for 12 hours. After the removal of the solvent from the dispersion, the mixture was pulverized and then calcined at 1250 °C in the air. Separately, glass powder A comprising 84wt% of lead oxide powder (PbO), 7 wt% of zinc oxide powder (ZnO) and 9 wt% of boron oxide powder (B 2 O 3 ) was prepared according to the usual method. To the calcined product prepared above, there were added 2 wt% of the glass powder A comprising PbO, ZnO and B 2 O 3 as well as 3 wt% of germanium oxide powder (GeO 2 ) and 1 wt% (corresponding to 0.4 wt% as expressed in terms of the amount of Li 2 O) of lithium carbonate powder (Li 2 CO 3 ), followed by introduction of the mixture into a ball mill together with ethanol and then wet blending for 48 hours. After the removal of the solvent from the dispersion, the mixture was pulverized, followed by addition of an appropriate amount of a polyvinyl alcohol solution to the pulverized product, drying the mixture, forming it into pellets having a diameter of 12 mm and a thickness of 4 mm and then firing the pellets at 955°C for 2 hours in the air. The composition of the product and the sintering temperature thereof are summarized in the following Table 3. The ceramic composition thus prepared was inspected for various characteristic properties which were determined under the same conditions used in Example 1. The results thus obtained are listed in the following Table 5. Examples 24 to 48 and Comparative Examples 13 to 26 The same procedures used in Example 23 were repeated except that the mixing ratio of barium carbonate, titanium oxide, neodymium oxide and samarium oxide; the kinds of glass powder as a minor component mainly comprising PbO, ZnO and B 2 O 3 in the ratio listed in Table 4 and the added amounts of the minor components were changed as detailed in Table 3 to prepare dielectric ceramic compositions and they were inspected for characteristic properties. The results thus obtained are summarized in Table 5. COMPOSITION OF DIELECTRIC CERAMIC BaO x TiO 2 y Nd 2 O 3 z SM 2 O 3 t GLASS POWDER wt% KIND OF GLASS GeO 2 wt% Li 2 O wt% CALCINATION TEMPERATURE °C EXAMPLE 23 0.13 0.70 0.17 0 2 A 3 0.4 955 24 0.18 0.67 0.11 0.04 7 A 3 0.2 930 25 0.18 0.67 0.11 0.04 10 A 3 0.2 900 26 0.18 0.67 0.11 0.04 15 A 3 0.2 885 27 0.16 0.67 0.11 0.06 20 A 2 0.4 855 28 0.18 0.66 0.13 0.03 5 B 5 0.4 970 29 0.17 0.67 0.10 0.06 10 B 3 0.8 940 30 0.16 0.65 0.17 0.02 15 B 3 0.4 910 31 0.13 0.70 0.17 0 7 A 3 0.4 930 32 0.13 0.70 0.15 0.02 7 A 3 0.4 925 33 0.13 0.70 0.12 0.05 7 A 3 0.4 925 34 0.14 0.71 0.04 0.11 10 A 5 0.2 930 35 0.17 0.66 0.17 0 10 A 5 0.2 915 36 0.17 0.66 0.17 0 10 A 7 0.2 910 37 0.17 0.66 0.17 0 10 A 1 0 0.2 930 38 0.16 0.65 0.18 0.01 7 A 3 0.2 935 39 0.16 0.65 0.18 0.01 7 A 3 0.4 915 40 0.16 0.65 0.18 0.01 7 A 3 0.6 905 41 0.16 0.65 0.18 0.01 7 A 3 0.8 885 42 0.15 0.67 0.18 0 10 A 5 0.4 880 43 0.15 0.67 0.18 0 15 A 3 0.4 850 44 0.17 0.66 0.17 0 20 C - - 950 45 0.16 0.67 0.17 0 18 D - - 940 46 0.16 0.67 0.17 0 20 E - - 940 47 0.16 0.66 0.18 0 17 F 5 0.3 850 48 0.17 0.67 0.10 0.06 10 B 3 0 960 COMPARATIVE EXAMPLE 13 0.05 0.75 0.19 0.01 10 A 5 0.2 945 14 0.30 0.57 0.11 0.02 10 A 3 0.2 930 15 0.08 0.86 0.05 0.01 15 A 3 0.4 890 16 0.15 0.45 0.39 0.01 9 A 2 0.6 900 17 0.11 0.57 0.31 0.01 10 A 2 0.8 890 18 0.10 0.89 0 0.01 10 A 2 0.4 910 19 0.14 0.55 0.01 0.30 5 A 3 0.4 920 20 0.15 0.70 0.13 0.02 0 - 0 0 1420 21 0.16 0.67 0.11 0.06 30 A 2 0.4 840 22 0.16 0.65 0.17 0.02 30 B 3 0.4 835 23 0.17 0.66 0.17 0 20 A 0 0.2 1150 24 0.15 0.70 0.13 0.02 10 A 15 0.4 840 25 0.17 0.66 0.17 0 20 G - - 900 26 0.15 0.70 0.13 0.02 19 H - - 900 KIND OF GLASS GLASS POWDER COMPOSITION (wt%) SOFTENING POINT (°C) A PbO (84) ZnO (7) B 2 O 3 (9) 315 B PbO (80) ZnO (10) B 2 O 3 (10) 310 C PbO (52) ZnO (4) B 2 O 3 (6) GeO 2 (31) Li 2 O (7) 417 D PbO (56) ZnO (5) B 2 O 3 (6) GeO2 (33) 480 E PbO (51) ZnO (4) B 2 O 3 (5) GeO 2 (30) Li 2 O (6) Sb 2 O 3 (4) 442 F PbO (74) PbF 2 (10) B 2 O 3 (9) ZnO (7) 275 G B 2 O 3 (35) SiO 2 (45) Al 2 O 3 (10) BaO (10) 650 H B 2 O 3 (24) SiO 2 (35) BaO (41) 690 ELECTRIC CHARACTERISTICS ε r Q τ f ppm/°C EXAMPLE 23 75.0 1590 37 24 77.0 1260 21 25 72.0 1110 10 26 70.5 925 6 27 69.0 660 4 28 78.0 1105 37 29 72.0 790 32 30 71.0 620 23 31 74.0 1310 31 32 73.5 1250 17 33 72.0 1000 -3 34 63.0 720 -16 35 70.0 1090 32 36 66.0 1100 27 37 61.0 980 21 38 73.0 1180 33 39 75.0 1120 42 40 78.0 1090 47 41 74.0 820 54 42 66.0 1150 -19 43 69.0 780 -20 44 60.0 850 5 45 61.5 920 -12 46 61.0 1000 16 47 68.0 1250 -8 48 70.0 750 -7 COMPARATIVE EXAMPLE 13 47.0 160 14 14 NO RESONANCE 15 68.0 310 166 16 41.0 210 76 17 45.0 100 36 18 65.0 320 110 19 44.0 280 -2 20 87.0 2870 18 21 31.0 210 19 22 26.0 160 31 23 96.0 100 85 24 43.0 250 -19 25 NO SINTERING 26 NO SINTERING Example 49 Barium carbonate powder (BaCO 3 ; 0.15 mole), titanium oxide powder (TiO 2 ; 0.675 mole), neodymium oxide powder (Nd 2 O 3 ; 0.13 mole), samarium oxide powder (Sm 2 O 3 ; 0.02 mole) and bismuth oxide powder (Bi 2 O 3 ; 0.025 mole) were charged in a ball mill together with ethanol and then subjected to wet blending for 12 hours. After the removal of the solvent from the dispersion, the mixture was pulverized and then calcined at 1100°C in the air. Separately, glass powder A comprising 84wt% of lead oxide powder (PbO), 7 wt% of zinc oxide powder (ZnO) and 9 wt% of boron oxide powder (B 2 O 3 ) was prepared according to the usual method. To the calcined product prepared above, there were added 2 wt% of the glass powder A comprising PbO, ZnO and B 2 O 3 , and 2 wt% of germanium oxide powder (GeO 2 ), followed by introducing the mixture into a ball mill together with ethanol and then wet blending for 12 hours. After the removal of the solvent from the dispersion, the mixture was pulverized, followed by addition of an appropriate amount of a polyvinyl alcohol solution to the pulverized product, drying the mixture, forming it into pellets having a diameter of 12 mm and a thickness of 4 mm and then firing the pellets at 1150 °C for 2 hours in the air. The composition of the product and the sintering temperature thereof are summarized in the following Table 6. The ceramic composition thus prepared was inspected for various characteristic properties which were determined under the same conditions used in Example 23. The results thus obtained are listed in the following Table 6. The ceramic composition thus prepared was processed into pieces each having a diameter of 7 mm and a thickness of about 3 mm and inspected for the specific dielectric constant ε r , the unloaded Q and the temperature coefficient τ f of the resonance frequency at a resonance frequency (ranging from 3 to 5 GHz) according to the dielectric resonance method. The results thus obtained are listed in the following Table 7. Examples 50 to 62 and Comparative Examples 27 to 45 The same procedures used in Example 49 were repeated except that the mixing ratio of barium carbonate, titanium oxide, neodymium oxide, samarium oxide and bismuth oxide; the kinds and the added amount of glass powder comprising PbO, ZnO and B 2 O 3 (glass powder B: 80 wt% PbO, 10 wt% ZnO and 10 wt% B 2 O 3 ) and the added amounts of the minor component GeO 2 as well as the added amount (d) of the third component were changed as detailed in Table 6 to prepare dielectric ceramic compositions and they were inspected for characteristic properties in the same manner used in Example 49. The results thus obtained are summarized in Table 7. ELECTRIC CHARACTERISTICS ε r Q τ f ppm/°C EXAMPLE 49 81.0 1150 7 50 74.0 930 -22 51 77.0 800 -12 52 77.0 1100 -13 53 78.0 950 -30 54 77.0 450 -14 55 76.0 820 -3 56 77.0 560 4 57 74.0 620 2 58 78.0 750 -8 59 80.0 1050 7 60 73.0 890 -21 61 74.0 720 -11 62 73.0 630 -17 COMPARATIVE EXAMPLE 27 51.0 120 -12 28 NO RESONANCE 29 70.0 400 130 30 41.0 170 33 31 49.0 80 -15 32 43.0 130 -35 33 80.0 130 -26 34 46.0 240 -38 35 79.0 1050 33 36 41.0 200 33 37 93.0 1200 5 38 33.0 180 -7 39 29.0 150 -5 40 85.0 1100 -33 41 45.0 200 -55 42 74.0 210 25 43 77.0 250 33 44 72.0 220 27 45 71.0 240 22 Example 63 Barium carbonate powder (BaCO 3 ; 0.13 mole), titanium oxide powder (TiO 2 ; 0.69 mole), neodymium oxide powder (Nd 2 O 3 ; 0.16 mole) and bismuth oxide powder (Bi 2 O 3 ; 0.02 mole) were charged in a ball mill together with ethanol and then subjected to wet blending for 12 hours. After the removal of the solvent from the dispersion, the mixture was pulverized and then calcined at 1250°C in the air. Separately, glass powder A comprising 84wt% of lead oxide powder (PbO), 7 wt% of zinc oxide powder (ZnO) and 9 wt% of boron oxide powder (B 2 O 3 ) was prepared according to the usual method. To the calcined product prepared above, there were added 2 wt% of the glass powder A comprising PbO, ZnO and B 2 O 3 , 3 wt% of germanium oxide powder (GeO 2 ) and 1 wt% (corresponding to 0.4 wt% as expressed in terms of the weight of Li 2 O) of lithium carbonate powder (Li 2 CO 3 ), followed by introduction of the mixture into a ball mill together with ethanol and then wet blending for 48 hours. After the removal of the solvent from the dispersion, the mixture was pulverized, followed by addition of an appropriate amount of a polyvinyl alcohol solution to the pulverized product, drying the mixture, forming it into pellets having a diameter of 12 mm and a thickness of 4 mm and then firing the pellets at 945°C for 2 hours in the air. The composition of the product and the sintering temperature thereof are summarized in the following Table 8. The ceramic composition thus prepared was processed into pieces each having a diameter of 7 mm and a thickness of about 3 mm and inspected for the specific dielectric constant ε r , the unloaded Q and the temperature coefficient τ f of the resonance frequency at a resonance frequency (ranging from 3 to 6 GHz) according to the dielectric resonance method. The results thus obtained are listed in the following Table 9. Examples 64 to 84 and Comparative Examples 46 to 59 The same procedures used in Example 63 were repeated except that the mixing ratio of barium carbonate, titanium oxide, neodymium oxide, samarium oxide and bismuth oxide; the kinds of glass powder comprising PbO, ZnO and B 2 O 3 (glass powder B: 80 wt% PbO, 10 wt% ZnO and 10 wt% B 2 O 3 ) and the added amounts of the minor components were changed as detailed in Table 8 to prepare dielectric ceramic compositions and they were inspected for characteristic properties. The results thus obtained are summarized in Table 9. COMPOSITION OF DIELECTRIC CERAMIC BaO x TiO 2 y Nd 2 O 3 z Sm 2 O 3 t Bi 2 O 3 w GLASS POWDER wt% KIND OF GLASS GeO 2 wt% Li 2 O wt% CALCINATION TEMPERATURE °C EXAMPLE 63 0.13 0.69 0.16 0 0.02 2 A 3 0.4 945 64 0.17 0.66 0.11 0.04 0.02 7 A 3 0.2 920 65 0.17 0.66 0.10 0.04 0.03 10 A 3 0.2 890 66 0.18 0.66 0.11 0.04 0.01 15 A 3 0.2 880 67 0.15 0.67 0.10 0.06 0.02 20 A 2 0.4 860 68 0.17 0.66 0.12 0.03 0.02 5 B 5 0.4 960 69 0.17 0.66 0.10 0.06 0.01 10 B 3 0.8 920 70 0.16 0.64 0.16 0.02 0.02 15 B 3 0.4 900 71 0.13 0.69 0.16 0 0.02 7 A 3 0.4 920 72 0.12 0.70 0.14 0.02 0.02 7 A 3 0.4 920 73 0.13 0.69 0.11 0.05 0.02 7 A 3 0.4 920 74 0.14 0.70 0.04 0.10 0.02 10 A 5 0.2 920 75 0.17 0.66 0.16 0 0.01 10 A 5 0.2 900 76 0.16 0.66 0.16 0 0.02 10 A 7 0.2 915 77 0.16 0.66 0.16 0 0.02 10 A 10 0.2 920 78 0.15 0.65 0.17 0.01 0.02 7 A 3 0.2 925 79 0.15 0.65 0.17 0.01 0.02 7 A 3 0.4 905 80 0.15 0.65 0.17 0.01 0.02 7 A 3 0.6 900 81 0.15 0.65 0.17 0.01 0.02 7 A 3 0.8 875 82 0.14 0.67 0.17 0 0.02 10 A 5 0.4 860 83 0.14 0.67 0.17 0 0.02 15 A 3 0.4 845 84 0.16 0.67 0.10 0.06 0.01 10 B 3 0 950 COMPARATIVE EXAMPLE 46 0.05 0.75 0.18 0.01 0.01 10 A 5 0.2 935 47 0.30 0.57 0.10 0.02 0.01 10 A 3 0.2 920 48 0.08 0.86 0.04 0.01 0.01 15 A 3 0.4 880 49 0.14 0.45 0.38 0.01 0.02 9 A 2 0.6 890 50 0.11 0.56 0.31 0.01 0.01 10 A 2 0.8 885 51 0.10 0.87 0 0.01 0.02 10 A 2 0.4 905 52 0.13 0.55 0.01 0.30 0.01 5 A 3 0.4 915 53 0.18 0.67 0.14 0.01 0 2 A 2 1.5 955 54 0.20 0.64 0.05 0.01 0.1 7 A 3 0.4 910 55 0.14 0.69 0.13 0.02 0.02 0 - 0 0 1400 56 0.15 0.67 0.11 0.06 0.01 30 A 2 0.4 850 57 0.15 0.65 0.16 0.02 0.02 30 B 3 0.4 820 58 0.16 0.66 0.16 0 0.02 20 A 0 0.2 1130 59 0.14 0.70 0.13 0.02 0.01 10 A 15 0.4 835 ELECTRIC CHARACTERISTICS ε r Q τ f ppm/°C EXAMPLE 63 76.0 1450 35 64 78.0 1160 18 65 73.0 1110 5 66 71.0 900 4 67 70.0 640 2 68 79.0 1050 35 69 73.0 760 29 70 81.0 1200 73 71 75.0 1250 29 72 74.0 1050 15 73 73.0 990 -5 74 64.0 730 -18 75 71.0 1100 30 76 67.0 1050 25 77 62.0 950 19 78 74.0 1080 30 79 76.0 1020 40 80 79.0 1050 43 81 75.0 800 50 82 68.0 1100 -22 83 70.0 790 -22 84 71.0 650 -10 COMPARATIVE EXAMPLE 46 49.0 170 13 47 NO RESONANCE 48 69.0 300 150 49 43.0 190 72 50 47.0 90 30 51 66.0 350 105 52 47.0 310 -5 53 60.0 390 47 54 47.0 180 -15 55 88.0 2770 15 56 35.0 240 23 57 29.0 170 29 58 97.0 120 75 59 45.0 230 -22 As has been discussed above in detail, the dielectric ceramic composition of the present invention exhibits excellent characteristic properties in that it has a large specific dielectric constant ε r , a large unloaded Q and a small temperature coefficient of the resonance frequency and the composition is advantageous in that it can be sintered at a low temperature and that it can easily be laminated together with, for instance, an Ag, Ag-Pd or Cu internal electrode.

Claims: A dielectric ceramic composition mainly comprising a major component which comprises barium, titanium, neodymium, samarium and oxygen and is represented by the following compositional formula: xBaO-yTiO 2 -zNd 2 O 3 -tSm 2 O 3 (wherein 0.1≦x≦0.2; 0.5≦y≦0.8; 0.01≦z≦0.2; 0≦t≦0.2, provided that x+y+z+t = 1 ); and a minor component mainly comprising glass powder, which mainly comprises PbO, ZnO and B 2 O 3 , and GeO 2 , and wherein the content (a) (% by weight) of the glass powder falls within the range of 1≦a≦25 and the content (b) (% by weight) of GeO 2 falls within the range of 0.5≦b≦10, on the basis of the weight of the major component. The dielectric ceramic composition of claim 1 which further comprises Li 2 O as a minor component and the content (c) (% by weight) of Li 2 O falls within the range of 0.04≦c≦4 on the basis of the weight of the major component. The dielectric ceramic composition of claim 1 or 2 which further comprises at least one member selected from the group consisting of Nb 2 O 5 , MnO, Al 2 O 3 and ZnO in an amount of up to 2% by weight. The dielectric ceramic composition of claim 1, 2 or 3 wherein the content of PbO, ZnO and B 2 O 3 in the glass powder are 5≦PbO≦90, 5≦B 2 O 3 ≦60, and O<ZnO≦65 (% by weight). The dielectric ceramic composition of claim 4 wherein the softening point of the glass powder is about 100 °C to about 500°C. A dielectric ceramic composition mainly comprising a major component which comprises barium, titanium, neodymium, samarium, bismuth and oxygen and is represented by the following compositional formula: xBaO-yTiO 2 -zNd 2 O 3 -tSm 2 O 3 -wBi 2 O 3 (wherein 0.1≦x≦0.2; 0.5≦y≦0.8; 0.01≦z≦0.2; 0.01 ≦t≦0.2; 0.005≦w≦0.05, provided that x+y+z+t+w = 1 ); and a minor component mainly comprising glass powder, which mainly comprises PbO, ZnO and B 2 O 3 , and GeO 2 , and wherein the content (a) (% by weight) of the glass powder falls within the range of 1≦a≦25 and the content (b) (% by weight) of GeO 2 falls within the range of 0.5≦b≦10 on the basis of the weight of the major component. The dielectric ceramic composition of claim 6 which further comprises Li 2 O as another minor component and the content (c) (% by weight) of Li 2 O falls within the range of 0.04≦c≦4 on the basis of the weight of the major component. The dielectric ceramic composition of claim 6 or 7 which further comprises at least one member selected from the group consisting of Nb 2 O 5 , MnO, Al 2 O 3 and ZnO in an amount of up to 2% by weight. The dielectric ceramic composition of claim 6, 7 or 8 wherein the content of PbO, ZnO and B 2 O 3 in the glass powder are 5≦PbO≦90, 5≦B 2 O 3 ≦60, and 0<ZnO≦65 (% by weight). The dielectric ceramic composition of claim 9 wherein the softening point of the glass powder is about 100 °C to about 500°C. A dielectric device such as a dielectric resonator and a dielectric filter, comprising a dielectric ceramic composition according to any one of claims 1 to 10.

Inventors: FUJINAGA MASATAKA, FUKUDA KOICHI, ISHITOBI SHINICHI, MITANI ATSUYUKI, TAKEDA MASATOSHI, FUJINAGA, MASATAKA, FUKUDA, KOICHI, ISHITOBI, SHINICHI, MITANI, ATSUYUKI, TAKEDA, MASATOSHI
Applicants: UBE INDUSTRIES, UBE INDUSTRIES, LTD.
Application year: 1995
Main classification: C04B35
IPC codes: C04B35, H01B3, H01G4