The present application relates to a magnesium oxide based dielectric ceramics with ultrahigh dielectric breakdown strength and a preparation method thereof. The composition of the magnesium oxide based dielectric ceramic material comprises: (1x)MgO-xAl.sub.2O.sub.3, wherein 0<x0.12 and x is a mole percentage. The material has a specific composite structure with magnesium aluminate spinel acting as a second phase surrounding a principal crystalline phase, MgO.

A spark plug according to one embodiment of the present invention includes an insulator formed of an alumina-based sintered body, wherein the insulator contains 90 wt % or more of an aluminum component in terms of oxide, and wherein crystal grains of the insulator has an average grain size of 1.5 mm or smaller and a grain size standard deviation of 1.2 m or smaller.

A heat-dissipating member includes aluminum oxide ceramics that includes crystal particles of aluminum oxide. The aluminum oxide ceramics includes 98 mass % or higher of aluminum in terms of Al.sub.2O.sub.3 with respect to 100 mass % of all constituents. The crystal particles have an average equivalent circle diameter of 1.6 m or more and 2.4 m or less. An equivalent circle diameter cumulative distribution curve of the crystal particles has a first diameter at 10 cumulative percent and a second diameter at 90 cumulative percent that is different from the first diameter by 2.1 m or more and 4.2 m or less.

A dielectric composition includes: a base material powder including (Ca.sub.1-xSr.sub.x) (Zr.sub.1-yTi.sub.y)O.sub.3 (0<x0.7, 0<y0.03); a first subcomponent including at least one selected from the group of an oxide of manganese (Mn) and a carbonate of manganese (Mn); a second subcomponent including at least one selected from the group of an oxide of yttrium (Y) and a carbonate of yttrium (Y), where a content of the second subcomponent is within a range from 2 to 3 mol, based on 100 mol of the base material powder; and a third subcomponent including at least one selected from the group of an oxide of silicon (Si) and a carbonate of silicon (Si), and an electronic component uses the same.

A cemented carbide including a hard phase, a binding phase, and inevitable impurities. The hard phase satisfies a first hard phase composed mainly of tungsten carbide, and a second hard phase composed mainly of a compound. The compound contains multiple types of metallic elements including tungsten and at least one element selected from carbon, nitrogen, oxygen, and boron. The second hard phase satisfies D10/D90<0.4, wherein D10 denotes a cumulative 10% grain size in an area-based grain size distribution on a surface or cross section of the cemented carbide, and D90 denotes a cumulative 90% grain size in the area-based grain size distribution, and satisfies .sup.2<5.0, wherein .sup.2 denotes the variance of the distance between the centroids of the nearest two of the second hard phases. The average grain size D.sub.W of the first hard phase ranges from 0.8 to 4.0 m and satisfies D.sub.M/D.sub.W<1.0, wherein D.sub.M denotes the average grain size of the second hard phase.

A multilayer electronic component includes a body including a plurality of dielectric layers, side margin portions disposed on the body, and external electrodes disposed on the body. The reliability of the multilayer electronic component is improved by controlling the contents of Si for each position of the dielectric layer and the side margin portion.

A support substrate 2 is a polycrystalline SiC substrate formed of polycrystalline SiC. Assuming that one of the two sides of the polycrystalline SiC substrate is a first side and that the other side is a second side, a substrate grain size change rate of the polycrystalline SiC substrate, which is a value obtained by dividing a difference between the average value of crystal grain sizes of the polycrystalline SiC on the first side and the average value of crystal grain sizes of the polycrystalline SiC on the second side by a thickness of the polycrystalline SiC substrate, is 0.43% or less. A radius of curvature of warpage of the polycrystalline SiC substrate is 142 m or more.

Polycrystalline cubic boron nitride, PCBN, material and methods of making PCBN. A method includes providing a matrix precursor powder comprising particles having an average particle size no greater than 250 nm, providing a cubic boron nitride, cBN, powder comprising particles of cBN having an average particle size of at least 0.2 intimately mixing the matrix precursor powder and the cBN powder,and sintering the intimately mixed powders at a temperature of at least 1100 C. and a pressure of at least 3.5 GPa to form the PCBN material comprising particles of cubic boron nitride, cBN dispersed in a matrix material.

The invention relates to a copper-ceramic composite comprising: a ceramic substrate; and a copper or copper alloy coating on the ceramic substrate, the copper or copper alloy having grain sizes of 10 m to 300 m.

The present invention relates to a copper-ceramic composite comprisinga ceramic substrate which contains aluminum oxide, the aluminum oxide having particle sizes in the range of 0.01 m to 25 m and a quantity distribution of the particle sizes with a median value d.sub.50 and an arithmetic mean value d.sub.arith, and the ratio of d.sub.50 to d.sub.arith being in the range of 0.75 to 1.10, a coating made of copper or a copper alloy provided on the ceramic substrate.