Stc, Inc

Standard Telephones and Cables Public Limited Company

Standard Telephones & Cables Limited

Dawn A Jackson

John H Alexander

Jennifer M Wheeler

A dielectric composition including a ternary system comprising non-stoichiometric lead magnesium niobate, non-stoichiometric lead zinc niobate and non-stoichiometric lead iron niobate, and a small amount of one or more oxide additives which serves to reduce the tan .delta. value in comparison with the ternary system alone. The one or more additives may be chosen from the group consisting of nickel oxide, stoichiometric lead nickel niobate, ceric oxide, lead oxide, zirconium oxide, silver oxide, manganese dioxide, lanthanum oxide and cobalt oxide. Compositions with firing temperatures in the range 950.degree. to 1100.degree. C. have dielectric constants in the range 10700 to 16600 (at 20.degree. C.) making the composition particularly useful for high silver content multilayer ceramic capacitors.

Dielectric composition

A dielectric composition comprising a ternary system of non-stoichiometric lead magnesium niobate, non-stoichiometric lead zinc niobate and non-stoichiometric lead iron niobate up to 10 wt % PbO may be added to the ternary mix. Compositions with firing temperatures in the range 950.degree. to 1040.degree. C., have dielectric constants in the range 13,900-22,100 making the composition particularly suitable for high silver content multilayer ceramic capacitors.

Ceramic capacitors and dielectric compositions

A dielectric composition, particularly suitable for the manufacture of ceramic capacitors, comprising lead magnesium niobate and lead zinc niobate. These may be additives, such as one or more oxide additives chosen from the group comprising silica, manganese dioxide, zinc oxide, nickel oxide, alumina, ceric oxide, lanthanum oxide and tungsten oxide, gallium oxide, titanium dioxide and lead oxide, or additives such as bismuth stannate. The compositions can be fired at temperatures between 980.degree. and 1075.degree. C. so that in the case of multilayer ceramic capacitors high silver content internal electrodes can be used. Higher dielectric constants, for example 9000 to 16,300, of the fired ceramics than conventional ceramics are obtained, thus permitting capacitor device size reduction.

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Old Harlow, United Kingdom

Dawn A Jackson