A rare earth aluminate sintered compact including rare earth aluminate phosphor crystalline phases and voids, wherein an absolute maximum length of 90% or more by number of rare earth aluminate phosphor crystalline phases is in a range from 0.4 μm to 1.3 μm, and an absolute maximum length of 90% or more by number of voids is in a range from 0.1 μm to 1.2 μm.

Certain embodiments of the present disclosure relate to ceramic materials with high thermal shock resistance and high erosion resistance. In one embodiment, a ceramic material is formed from a composition comprising Al.sub.2O.sub.3, MgO, SiO.sub.2.

A light-emitting ceramic and a light-emitting device. The light-emitting ceramic comprises a YAG substrate and light-emitting centers and diffusion particles evenly dispersed in the YAG substrate. The light-emitting centers are lanthanide-doped YAG fluorescent powder particles of 10-20 μm in grain size. The particle size of the scattering particles is 20-50 nm. The YAG substrate is a lanthanide-doped YAG ceramic. Also, the grain size of the YAG substrate is less than the grain size of the YAG fluorescent powder particles.

A sintered Ni ferrite body having a composition comprising, calculated as oxide, 47.0-48.3% by mol of Fe.sub.2O.sub.3, 14.5% or more and less than 25% by mol of ZnO, 8.2-10.0% by mol of CuO, and more than 0.6% and 2.5% or less by mol of CoO, the balance being NiO and inevitable impurities, and having an average crystal grain size of more than 2.5 μm and less than 5.5 μm.

Various shaped abrasive particles are disclosed. Each shaped abrasive particle includes a body having at least one major surface and a side surface extending from the major surface.

A wavelength converter is provided with a light-transmitting substrate and with a thin film that is formed on a surface of the light-transmitting substrate and that contains a phosphor. A sintered body that constitutes the light-transmitting substrate has an average particle size of 5-40 μm. The light-transmitting substrate contains at least 10-500 ppm by mass of MgO. The principal component of the phosphor is an α-sialon that is indicated by the general formula (Ca.sub.α,Eu.sub.β) (Si,Al).sub.12(O,N).sub.16 (provided that 1.5<α+β<2.2, 0<β<0.2, and O/N≦0.04).

A cubic boron nitride sintered body has between 50% and 75% cubic boron nitride by volume and between 25% and 50% binder phase by volume, and inevitable impurities. The binder phase contains an Al compound and a Zr compound. The Al compound contains Al and one or more of N, O and B; and the Zr compound contains Zr and one or more of C, N, O and B. At a polished surface of the cubic boron nitride sintered body, 40% or more of the Zr compounds satisfy the ratio 0.25≦n/N≦0.8, where: N represents the number of line segments drawn radially at equal intervals from a center of gravity of a given Zr compound to a boundary with a non-Zr compound; and n represents the number among those N line segments which intersect a boundary between the given Zr compound and cubic boron nitride.

A method for preparing a boron carbide material includes: providing raw materials of a boron material, a carbon material and a rare earth oxide, wherein an element molar ratio B:C of the boron material to the carbon material is in a range of 4:1 to 4:7, and the rare earth oxide is in an amount of 5 wt % or less based on a total weight of the raw materials, mixing and milling the raw materials to obtain a mixture, compressing the mixture into a tablet form by a tablet press, and sintering the compressed mixture by a laser, wherein the laser has a laser wavelength of 980 nm, a laser power in a range of 100 to 3000 W, and a laser irradiation time of 3 to 60 s.

A cutting tool comprises a rake face and a flank face, the cutting tool being composed of a substrate made of a cubic boron nitride sintered material and a coating provided on the substrate, the coating including a MAlN layer, the MAlN layer including crystal grains of M.sub.xAl.sub.1-xN in the cubic crystal system, n.sub.F<n.sub.R being satisfied, where n.sub.F represents a number of voids per 100 μm in length of the MAlN layer on the flank face in a cross section of the MAlN layer, and n.sub.R represents a number of voids per 100 μm in length of the MAlN layer on the rake face in a cross section of the MAlN layer, n.sub.D being 3 or less, where n.sub.D represents a number of droplets per 100 μm in length of the MAlN layer on the flank face in a cross section of the MAlN layer.

A silicon carbide porous body contains β-SiC particles, Si particles, and metal silicide particles. The maximum particle diameter of the β-SIC particles is not smaller than 15 μm. The content of the Si particles is not lower than 10 mass %. The maximum particle diameter of the Si particles is not larger than 40 μm. Further, an oxide coating film having a thickness not smaller than 0.01 μm and not larger than 5 μm is provided on surfaces of the Si particles.