The sliding member according to the embodiment includes a silicon nitride sintered body that includes silicon nitride crystal grains and a grain boundary phase, in which a percentage of a number of the silicon nitride crystal grains including dislocation defect portions inside the silicon nitride crystal grains among any 50 of the silicon nitride crystal grains having completely visible contours in a 50 μm×50 μm observation region of any cross section or surface of the silicon nitride sintered body is not less than 0% and not more than 10%. The percentage is more preferably not less than 0% and not more than 3%.

A turbine assembly includes an axial turbine with an axially arranged series of rotor sections and an external sheath providing structural support for the axial turbine, wherein the sheath is made from dense silicon nitride. Each rotor section includes an outer ring and rotor blades and the outer rings of the rotor sections connect to form a rotating outer casing, wherein the rotor sections are made from reaction bonded silicon nitride.

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.

A method is disclosed for forming a blended phosphor composition. The method includes the steps of firing precursor compositions that include europium and nitrides of at least calcium, strontium and aluminum, in a refractory metal crucible and in the presence of a gas that precludes the formation of nitride compositions between the nitride starting materials and the refractory metal that forms the crucible. The resulting compositions can include phosphors that convert frequencies in the blue portion of the visible spectrum into frequencies in the red portion of the visible spectrum.

An insert may include a sintered silicon nitride including -Si.sub.3N.sub.4 as a main component. The area up to 0.5 mm deep from a surface of the sintered silicon nitride is a first region. The first region may include an oxygen content of less than 0.8% by mass. The first region may include ReMgSi.sub.2O.sub.5N (Re is at least one of Yb and Y). A cutting tool may include a holder that extends from a first end toward a second end and includes a pocket on a side of the first end, and the insert located at the pocket.

A method is disclosed for forming a blended phosphor composition. The method includes the steps of firing precursor compositions that include europium and nitrides of at least calcium, strontium and aluminum, in a refractory metal crucible and in the presence of a gas that precludes the formation of nitride compositions between the nitride starting materials and the refractory metal that forms the crucible. The resulting compositions can include phosphors that convert frequencies in the blue portion of the visible spectrum into frequencies in the red portion of the visible spectrum.

A turbine assembly includes an axial turbine with an axially arranged series of rotor sections and an external sheath providing structural support for the axial turbine, wherein the sheath is made from dense silicon nitride. Each rotor section includes an outer ring and rotor blades and the outer rings of the rotor sections connect to form a rotating outer casing, wherein the rotor sections are made from reaction bonded silicon nitride.

Provided are a method for producing a ceramic composite material that has a high light emission intensity, a ceramic composite material, and a light emitting device. The method for producing a ceramic composite material, includes: preparing a green body containing a nitride fluorescent material having a composition represented by the following chemical formula (I) and aluminum oxide particles mixed with each other; and performing primary sintering the green body at a temperature in a range of 1,250 C. or more and 1,600 C. or less to provide a first sintered body:

M.sub.wLn.sup.1.sub.xA.sub.yN.sub.z(I)

wherein in the chemical formula (I), M represents at least one element selected from the group consisting of Ce and Pr; Ln.sup.1 represents at least one element selected from the group consisting of Sc, Y, La, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu; A represents at least one element selected from the group consisting of Si and B; and w, x, y, and z each satisfy 0<w1.0, 2.5x3.5, 5.5y6.5, and 10z12.

When a large-sized silicon nitride substrate having high thermal conductivity is produced, a portion where the thermal conductivity is low is generated, which causes reduction in yield (pass rate). Provided is a silicon nitride substrate in which ?e/?c, which is a ratio of a thermal conductivity ?c at a center portion of the substrate to a thermal conductivity ?e at an end portion of the substrate, is 0.85 to 1.15. Preferably, the silicon nitride substrate has a size of 150 mm?150 mm or more. In the silicon nitride substrate, the ?c and the ?e each are preferably 100 W/m.Math.K or more.

A method is disclosed for forming a blended phosphor composition. The method includes the steps of firing precursor compositions that include europium and nitrides of at least calcium, strontium and aluminum, in a refractory metal crucible and in the presence of a gas that precludes the formation of nitride compositions between the nitride starting materials and the refractory metal that forms the crucible. The resulting compositions can include phosphors that convert frequencies in the blue portion of the visible spectrum into frequencies in the red portion of the visible spectrum.