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AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsYoshihiro Matsuo, Gen Itakura, Shoichi Ikebe, Tatsuya Wada
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Grain boundary layer dielectric ceramic compositions comprising semiconductive ceramic grains having a composition of 50.23 to 49.47 mol % of SrO and CaO, 49.72 to 50.23 mol % of TiO.sub.2, 0.05 to 0.3 mol % of Nb.sub.2 O.sub.5, substantially each of said grains being surrounded by grain boundary layer dielectric materials which are formed by grain boundary diffusion of a mixture having a composition of 93.5 to 8.5 mol % of Bi.sub.2 O.sub.3, 4.5 to 45 mol % of Cu.sub.2 O, 0.5 to 4 mol % of MnO.sub.2, 1 to 8.5 mol % of B.sub.2 O.sub.3, 0.5 to 17 mol % of La.sub.2 O.sub.3, and below 17 mol % of TiO.sub.2. These ceramic compositions provide capacitors having a temperature coefficient of capacitance less than .+-.15%, an apparent dielectric constant higher than 35,000, a dielectric loss less than 0.01 and a breakdown voltage higher than 500 V/mm; or capacitors having a temperature coefficient of capacitance less than .+-.10%, an apparent dielectric constant higher than 20,000, a dielectric loss less than 0.01 and a breakdown voltage higher than 700 V/mm; or capacitors having a temperature coefficient of capacitance less than .+-.5%, an apparent dielectric constant higher than 5,000, a dielectric loss less than 0.01 and a breakdown voltage higher than 700 V/mm.
A grain boundary layer dielectric ceramic composition comprising semiconductive ceramic grains having a composition of 50.23 to 49.47 mol% of SrO, 49.72 to 50.23 mol% of TiO.sub.2, and 0.05 to 0.3 mol% of Nb.sub.2 O.sub.5, substantially each of said grains being surrounded by a grain boundary layer of dielectric material formed by grain boundary diffusion of a mixture consisting of 93.5 to 8.5 mol% of Bi.sub.2 O.sub.3, 4.5 to 45 mol% of Cu.sub.2 O, 0.5 to 4 mol% of MnO.sub.2, 1 to 8.5 mol% of B.sub.2 O.sub.3, 0.5 to 17 mol% of La.sub.2 O.sub.3, and less than 17 mol% of TiO.sub.2, characterized in having a temperature coefficient of capacitance lower than said composition recited above absent La.sub.2 O.sub.3 in said grain boundary diffusion mixture.
A grain boundary layer dielectric ceramic composition comprising semiconductive ceramic grains having a composition of 50.23 to 49.47 mol% of SrO and CaO, wherein the amount of CaO is less than 22.26 mol%, 49.72 to 50.23 mol% of TiO.sub.2 and 0.05 to 0.3 mol% of Nb.sub.2 O.sub.5, substantially each of said grains being surrounded by a grain boundary layer of dielectric material formed by grain boundary diffusion of a mixture consisting of 93.5 to 8.5 mol% of Bi.sub.2 O.sub.3, 4.5 to 45 mol% of Cu.sub.2 O, 0.5 to 4 mol% of MnO.sub.2, 1 to 8.5 mol% of B.sub.2 O.sub.3, 0.5 to 17 mol% of La.sub.2 O.sub.3, and less than 17 mol% of TiO.sub.2, characterized in having a temperature coefficient of capacitance lower than said composition recited above absent La.sub.2 O.sub.3 in said grain boundary diffusion mixture.
A grain boundary layer dielectric ceramic composition comprising semiconductive ceramic grains having a composition of 100 mol parts of a mixture of 50.23 to 49.47 mol% of SrO and CaO, wherein the amount of CaO is less than 22.26 mol%, 49.72 to 50.23 mol% of TiO.sub.2, and 0.05 to 0.3 mol% of Nb.sub.2 O.sub.5, and containing SiO.sub.2 in an amount less than 2 mol parts of SiO.sub.2 to 100 mol parts of said mixture, substantially each of said grains being surrounded by a grain boundary layer of dielectric material formed by a grain boundary diffusion of a mixture consisting of 93.5 to 8.5 mol% of Bi.sub.2 O.sub.3, 4.5 to 45 mol% of Cu.sub.2 O, 0.5 to 4 mol% of MnO.sub.2, 1 to 8.5 mol% of B.sub.2 O.sub.3, 0.5 to 17 mol% of La.sub.2 O.sub.3, and less than 17 mol% of TiO.sub.2, characterized in having a temperature coefficient of capacitance lower than said composition recited above absent La.sub.2 O.sub.3 in said grain boundary diffusion mixture.
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