The object of the present invention is to provide a dielectric ceramic composition having good properties, particularly good IR property and high temperature accelerated lifetime.

The dielectric ceramic composition of the present invention has a main component made of a perovskite type compound expressed by a compositional formula of (Ba.sub.1-x-ySr.sub.xCa.sub.y).sub.m(Ti.sub.1-zZr.sub.z)O.sub.3 (note that, m, x, y, and z of the above compositional formula all represent molar ratios, and each satisfies 0.9m1.1, 0x0.5, 0y0.3, 0(x+y)0.6, and 0.03z0.3), and

a first sub component made of an oxide of a rare earth element R (note that, R is at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), wherein

the dielectric ceramic composition includes a dielectric particle and a particle boundary, and the dielectric particle include a complete solid solution particle in which Zr is solid dissolved to the entire dielectric particle,

when Za represents a concentration of Zr in the dielectric ceramic composition in case a concentration of Ti atom in the dielectric ceramic composition is deemed to be 100 atom % and when Zb represents an average concentration of Zr in the complete solid solution particle in case a concentration of Ti atom in the complete solid solution particle is deemed to be 100 atom %,

0.7<(Zb/Za) is satisfied, and

a standard deviation and an average value of the Zb measured satisfies

(the standard deviation/the average value)0.15.

A dielectric ceramic composition having good properties, particularly good IR property and high temperature accelerated lifetime, even under high electric field intensity. A dielectric ceramic composition having a main component made of a perovskite type compound expressed by a compositional formula of (Ba1-x-ySrxCay)m(Ti1-zZrz)O3 (note that, m, x, y, and z of the above compositional formula all represent molar ratios, and each satisfies 0.9<m<1.1, 0<x<0.5, 0<y<0.3, 0<(x+y)<0.6, and 0.03<z<0.3), and a first sub component made of an oxide of a rare earth element R (note that, R is at least one selected from the group consisting of Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu), wherein the dielectric ceramic composition includes dielectric particles and a particle boundary.

A ceramic capacitor includes a multilayer structure, wherein a main component of dielectric layers is ceramic expressed by a general formula A.sub.mBO.sub.3 (0.995m1.010), wherein the dielectric layers include a rare earth element Re as a first sub-component by 2.0 mol to 5.0 mol when converted into Re.sub.2O.sub.3/2, include Mg as a second sub-component by 1.0 mol to 3.0 mol when converted into MgO, include V as a third sub-component by 0.05 mol to 0.25 mol when converted into V.sub.2O.sub.5/2, include Si as a fourth sub-component by 0.5 mol to 5.0 mol when converted into SiO.sub.2, include an alkali earth metal element M as a fifth sub-component by 0.1 mol to 5.0 mol when converted into MCO.sub.3, on a presumption that an amount of the ceramic is 100 mol, wherein a ratio Si/V is 30 or less.

The present disclosure is related to a method of producing a fired ceramic article. The method may include: heating a ceramic green body in a kiln, and controlling oxygen concentration in the kiln such that the oxygen concentration swings during the heating of the ceramic green body.

A method for fabricating a ceramic material includes impregnating a porous structure with a mixture that includes a preceramic polymer and a filler. The filler includes at least one free metal. The preceramic polymer material is then rigidized to form a green body. The green body is then thermally treated to convert the rigidized preceramic polymer material into a ceramic matrix located within pores of the porous structure. The same thermal treatment or a second, further thermal treatment is used to cause the at least one free metal to move to internal porosity defined by the ceramic matrix or pores of the porous structure.

A silicon nitride substrate including silicon nitride crystal grains and a grain boundary phase and having a thermal conductivity of 50 W/m.Math.K or more, wherein, in a sectional structure of the silicon nitride substrate, a ratio (T2/T1) of a total length T2 of the grain boundary phase in a thickness direction with respect to a thickness T1 of the silicon nitride substrate is 0.01 to 0.30, and a variation from a dielectric strength mean value when measured by a four-terminal method in which electrodes are brought into contact with a front and a rear surfaces of the substrate is 20% or less. The dielectric strength mean value of the silicon nitride substrate can be 15 kV/mm or more. According to above structure, there can be obtained a silicon nitride substrate and a silicon nitride circuit board using the substrate in which variation in the dielectric strength is decreased.

The present invention is directed to a porous pre-densified CeO.sub.2 stabilized ZrO.sub.2 ceramic having a density of 50.0 to 95.0%, relative to the theoretical density of zirconia, and an open porosity of 5 to 50% as well as to ceramic having a density of 97.0 to 100.0%, relative to the theoretical density of zirconia, and wherein the grains of the ceramic have an average grain size of 50 to 1000 nm, methods for the preparation of the pre-densified and densified ceramics and their use for the manufacture of dental restorations.

A glass-ceramic-ferrite composition contains glass, a ceramic filler, and NiZnCu ferrite. The glass contains about 0.5% by weight or more of R.sub.2O, where R is at least one selected from the group consisting of Li, Na, and K; about 5.0% by weight or less of Al.sub.2O.sub.3; about 10.0% by weight or more of B.sub.2O.sub.3; and about 85.0% by weight or less of SiO.sub.2 on the basis of the weight of the glass. The NiZnCu ferrite accounts for about 58% to 64% by weight of the glass-ceramic-ferrite composition. The ceramic filler contains quartz and, in some cases, forsterite. The quartz accounts for about 4% to 13% by weight of the glass-ceramic-ferrite composition. The forsterite accounts for about 6% by weight or less of the glass-ceramic-ferrite composition.

A ceramic electronic device includes: a multilayer structure; and a cover layer, wherein a concentration of Mn of the cover layer with respect to a main component ceramic is larger than a concentration of Mn of the dielectric layers with respect to a main component ceramic in a capacity section, wherein an average crystal grain diameter of a first dielectric layer is smaller than that of a second dielectric layer, and a concentration of Mn of the first dielectric layer with respect to the main component ceramic is larger than a concentration of Mn of the second dielectric layer with respect to the main component ceramic, in the capacity section.

Methods of producing a ceramic article include heating the ceramic green body containing a quantity of one or more organic materials to extract only a fraction of the organic materials from the ceramic green body by exposing the ceramic green body to a process atmosphere which is heated to a hold temperature of from 225? C. to about 400? C. and has from 2% to 7% O.sub.2 by volume of the process atmosphere. The method further includes cooling the ceramic green body to a temperature of below 200? C., exposing the ceramic green body to a higher concentration of O.sub.2 than in the process atmosphere of the heating step, and firing the ceramic green body to form the ceramic article. Volatile extraction units for implementing the methods are also described.