Provided is a composite ceramic layered body, including: a substrate; and a composite ceramic that coats the substrate, the composite ceramic including a nitride phase and an oxide phase having an elastic modulus that differs from an elastic modulus of the nitride phase by 10% or more. The composite ceramic includes, among the nitride phase and the oxide phase, a first phase that occupies a largest area ratio, and a toughening phase that occupies an area ratio of 1% or more and has a largest difference in elastic modulus from an elastic modulus of the first phase. In a case in which the first phase is the nitride phase, the toughening phase is the oxide phase, and in a case in which the first phase is the oxide phase, the toughening phase is the nitride phase.

Methods for producing wavelength converters are described. The methods include sintering a mixture consisting essentially of first particles and second particles to form a sintered article. In embodiments the first particles consist essentially of particles of -SiAlON or precursors thereof, and the second particles consist essentially one or more sintering aids or precursors thereof. In embodiments the sintered article has a density that is greater than or equal to about 90% of a theoretical bulk density of the mixture, and is configured to convert primary light incident thereon to secondary light, wherein the secondary light exhibits a peak with a full width half maximum of greater than 0 to about 60 nanometers (nm) within a wavelength range of about 495 nm to about 600 nm.

A process for producing a silicon nitride powder characterized by comprising a step of providing a starting material powder containing not less than 90% by mass of a silicon powder; the step of filling a heat-resistant reaction vessel with the starting material powder; a step of obtaining a massive product thereof by a combustion synthesis reaction by igniting the starting material powder filled in the reaction vessel in a nitrogen atmosphere and permitting a heat of nitriding combustion of silicon to propagate to the whole starting material powder; and a step of mechanically milling the massive product by a dry method.

Ceramic composite materials that are reinforced with carbide fibers can exhibit ultra-high temperature resistance. For example, such materials may exhibit very low creep at temperatures of up to 2700 F. (1480 C.). The present composites are specifically engineered to exhibit matched thermodynamically stable crystalline phases between the materials included within the composite. In other words, the reinforcing fibers, a debonding interface layer disposed over the reinforcing fibers, and the matrix material of the composite may all be of the same crystalline structural phase (all hexagonal), for increased compatibility and improved properties. Such composite materials may be used in numerous applications.

A tape casting slurry composition for preparing a silicon nitride sintered body is provided. The tape casting slurry composition exhibits a viscosity suitable for tape casting, and thus, can easily control the area and thickness of the prepared green sheet, thereby preparing a large area silicon nitride sintered body having a thickness of a circuit board without post-processing processes such as grinding, and the like. Therefore, according to the present invention, a silicon nitride sintered body can be prepared using low cost raw materials by a simplified process, thereby securing efficiency and economic feasibility of the preparation process.

Disclosed are ceramic powder compositions that include Si, N, O, C, Mg, and/or Mn in tailored combinations of different crystalline phases for producing high temperature resistant and high strength ceramic products. In some aspects, a ceramic powder for producing high temperature-resistant and/or high mechanical strength materials comprises a silicon nitride (Si.sub.3N.sub.4) powder, comprising Si.sub.3N.sub.4 particles having a size within a range of 30 nm to 700 nm, wherein the Si.sub.3N.sub.4 powder include alpha and beta phase silicon nitride in an amount up to about 1-100% vol; and an impurity constituent intermixed with the Si.sub.3N.sub.4 powder within the ceramic powder, the impurity constituent comprising at least one of silicon (Si), nitrogen (N), oxygen (O), carbon (C), magnesium (Mg), or manganese (Mn), wherein the impurity constituent constitutes less than about 0.1% wt to 15% wt of the ceramic powder.

A sintered material includes a first material and a second material, the first material being partially stabilized ZrO.sub.2 having a crystal grain boundary or crystal grain in which 5 to 90 volume % of Al.sub.2O.sub.3 is dispersed with respect to a whole of the first material, the second material including at least one of SiAlON, silicon nitride and titanium nitride, the sintered material including 1 to 50 volume % of the first material.

A silicon nitride powder having a specific surface area of 4.0 to 9.0 m.sup.2/g, a phase proportion of less than 40 mass %, and an oxygen content of 0.20 to 0.95 mass %, wherein a frequency distribution curve obtained by measuring a volume-based particle size distribution by a laser diffraction scattering method has two peaks, peak tops of the peaks are present respectively at 0.4 to 0.7 m and 1.5 to 3.0 m, a ratio of frequencies of the peak tops ((frequency of the peak top in a particle diameter range of 0.4 to 0.7 m)/(frequency of the peak top in a particle diameter range of 1.5 to 3.0 m)) is 0.5 to 1.5, and a ratio D50/D.sub.BET (m/m) of a median diameter D50 (m) determined by the measurement of particle size distribution to a specific surface area-equivalent diameter D.sub.BET (m) calculated from the specific surface area is 3.5 or more.

A production process for a crystal oriented ceramics includes: a first step of preparing composite particles formed of particles having magnetic anisotropy having magnetic susceptibility anisotropy and seed particles having magnetic susceptibility anisotropy less than or equal to 1/10 of the magnetic susceptibility anisotropy of the particles having magnetic anisotropy and are formed of an inorganic compound having an anisotropic shape in which a crystal axis intended to be corresponds to a minor axis or a major axis; a second step of adding raw material powder including the composite particles to a solvent to prepare a slurry a third step of preparing a green compact by disposing the slurry in a static magnetic field of 0.1 tesla and drying the slurry in a state in which crystal axes of the seed particles in a major axis direction are in one direction; and a fourth step of sintering the green compact.

A cBN material and a method of making a cBN material, the method including the steps of providing a powder mixture comprising cBN grains, aluminum and a Ti(CxNyOz)a powder, subjecting the powder mixture to a milling to form a powder blend, subjecting the powder blend to a forming operation to form a green body, subjecting the green body to a pre-sintering step, at a temperature between 650 to 950 C., to form a pre-sintered body, and subjecting the pre-sintered body to a HPHT operation to form the cBN material. For the Ti(CxNyOz)a powder, 0.05z0.4. In addition, a cBN material includes cBN grains, an Al2O3 phase, a binder phase of TiC, TiN and/or TiCN, W and Co, whereby a quotient Q is <0.25 of the cBN material.