Sprague Electric Company

Ian Burn

Stephen M Neirman

A ceramic slurry or slip includes ceramic powder, an organic plasticizer and a resin binder combined in an aromatic hydrocarbon solvent and has a viscosity that is independent of shear rate. Monolithic ceramic capacitors having fewer pin holes are made by forming a falling sheet of this Newtonian slip, and repeatedly interrupting the falling curtain by passing a carrier through it to form layers of green ceramic. An electroding film is deposited on each green ceramic layer to form buried electrodes. The Newtonian slip is advantageously self leveling and contains relatively few pin holes that degrade capacitor performance.

Newtonian ceramic slip and process for using

Formulations for a variety of air sintered ceramic barrier layer capacitors are provided wherein from 0.3 to 1.7 mole % of donor material is added to a strontium titanate and the relative amounts of strontium and titanium have been adjusted so that large-small cation balance and charge balance may be achieved by strontium vacancies, e.g. ##EQU1## These low cost materials have large grains and exhibit high dielectric constants.

SrTiO.sub.3 barrier layer capacitor

A donor modified strontium titanate formulated to become conductive when sintered in air, is further modified with a minute quantity of manganese and sintered to maturity in a nitrogen atmosphere. A paste including silver particles, and oxides of bismuth and copper is applied to two major portions of the body. The coated body is heated at about 920.degree. C. to oxidize the grain boundaries and to form silver electrodes tightly adhered to the body.

Method for making a ceramic intergranular barrier-layer capacitor

Monolithic capacitors having Q's of 3500 include copper electrodes buried in a non-reducible body that consists of a crystalline magnesium titanate phase and an intergranular glass phase. The crystalline phase contains magnesium meta-titanate and/or ortho-titanate. Magnesium di-titanate is excluded from the body as are the oxides of lead, bismuth and cadmium, which materials are reducible at the firing conditions necessary to preserve the integrity of the copper electrodes.

High Q monolithic capacitor with glass-magnesium titanate body

The ceramic body of a monolithic ceramic capacitor consists of a granular barium titanate phase and a relatively low temperature melting intergranular phase. The body is capable of exhibiting a very high dielectric constant, e.g., over 5000, a Curie temperature of near 25.degree. C., and may be fired to maturity at 1150.degree. C. or lower and contain low cost buried electrodes. These properties obtain from a narrow range of compositions for which charge balance and large/small cation stoichiometry in the total formulation are found to be very critical. Cd, Zn, Cu, Li and Na are found to enter the grains as large acceptor cations on Ba sites and may be charge compensated by the small donor cations of charge +5, Bi, Sb, Nb and Ta or by the small donor cations of charge +6, W and Mo, on the Ti sites. At least 0.3 mole percent of glass-former cations are desirable for establishing a low melting flux during sintering but more than 2.2 mole percent glass-formers tends to reduce the dielectric constant.

Low firing monolithic ceramic capacitor with high dielectric constant

A monolithic ceramic capacitor having buried nickel electrodes is made by forming a paint of alkaline earth zirconates, a boron containing powder and an organic vehicle and binder. Nickel containing films are buried between dried and stacked layers of the paint. The stack is fired in a partial oxygen atmosphere at from 1200.degree. C. to 1400.degree. C. to produce a fully densified ceramic having a dielectric constant of greater than 30 and to provide a nickel electroded monolithic capacitor having a Q of greater than 1000 and a TCC of between .+-.30 ppm/.degree.C. or better.

Monolithic capacitor with low firing zirconate and nickel electrodes

Powders of barium titanate, of an alkaline-earth-zirconate and of a cadmium containing glass are mixed with an organic binder to form a body that is subsequently fired at from 1800.degree. F to 2050.degree. F to make a glass-reacted-ceramic dielectric having a glass phase intermixed with a single titanate-zirconate phase. The omission of the conventional calcining step to obtain the single phase titanate-zirconate results in a substantial cost saving.

Method for making a glass-reacted-ceramic

A monolithic ceramic capacitor has base-metal electrodes buried in a high dielectric constant reduction resistant glass-ceramic body. The glass component is an alkaline earth aluminoborate glass. The ceramic component is a barium titanate. The capacitor body is sintered at from 950.degree. C to 1080.degree. C in a low partial oxygen atmosphere. The buried electrode may be elementary copper.

Monolithic base-metal glass-ceramic capacitor

A monolithic ceramic capacitor having base metal electrodes is described that meets the standard TCC limits of .+-. 15% from -55.degree. C to 125.degree. C. The ceramic includes small quantities of acceptor dopants, particularly manganese added to barium titanate and an alkali-earth-metal-zirconate. When fired from 1250.degree. C to 1400.degree. C in a partial oxygen atmosphere of 10.sup..sup.-7 to 10.sup..sup.-9 atmospheres of oxygen, a liquid phase sintering occurs during which the titanate-zirconate grains do not grow and there is formed a concentration gradient of the zirconate near the grain surfaces while a liquid manganese titanate forms a second and immiscible phase in the grain boundary regions.

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Williamstown, MA, United States of America

Ian Burn