Abstract: A high pressure phase spinel type sialon represented by the chemical formula Si6−xAlxOxN8−x (0<x≦4.2), and a high pressure phase spinel type silicon oxynitride represented by the chemical formula Si3+xO2xN4 (═Si3N4.xSiO2, 0<x<1). Methods for their production by instantaneous pressing by means of an impulse wave.

Abstract: A silicon nitride sintered product comprising silicon nitride grains and a grain boundary phase, wherein the grain boundary phase consists essentially of a single phase of a Lu4Si2O7N2 crystal phase, and the composition of the silicon nitride sintered product is a composition in or around a triangle ABC having point A: Si3N4, point B: 28 mol % SiO2-72 mol % Lu2O3 and point C: 16 mol % SiO2-84 mol % Lu2O3, as three apexes, in a ternary system phase diagram of a Si3N4—SiO2—Lu2O3 system. Also disclosed is a silicon nitride sintered product comprising silicon nitride grains and a grain boundary phase of an oxynitride, wherein the composition of the sintered product is a composition in a triangle having point A: Si3N4, point B: 40 mol % SiO2-60 mol % Lu2O3 and point C: 60 mol % SiO2-40 mol % Lu2O3, as three apexes, in a ternary system phase diagram of a Si3N4—SiO2—Lu2O3 system.

Abstract: An oxynitride phosphor activated by a rare earth element, represented by the formula MexSi12−(m+n)Al(m+n)OnN16−n:Re1yRe2x, wherein a part or all of metal Me (where Me is at least one metal selected from the group consisting of Ca, Mg, Y and lanthanide metals excluding La and Ce) in &agr;-sialon solid solution, is substituted by lanthanide metal Re1 (where Re1 is at least one metal selected from the group consisting of Ce, Pr, Eu, Tb, Yb and Er), or two lanthanide metals Re1 and a coactivator Re2 (where Re2 is Dy), to be an emission center.

Abstract: A silicon nitride sintered product comprising silicon nitride grains and a grain boundary phase, wherein the grain boundary phase consists essentially of a single phase of a LU4Si2O7N2 crystal phase, and the composition of the silicon nitride sintered product is a composition in or around a triangle ABC having point A: Si3N4, point B: 28 mol % SiO2-72 mol % LU2O3 and point C: 16 mol % SiO2-84 mol % LU2O3, as three apexes, in a ternary system phase diagram of a Si3N4—SiO2—LU2O3 system. Also disclosed is a silicon nitride sintered product comprising silicon nitride grains and a grain boundary phase of an oxynitride, wherein the composition of the sintered product is a composition in a triangle having point A: Si3N4, point B: 40 mol % SiO2-60 mol % LU2O3 and point C: 60 mol % SiO2-40 mol % LU2O3, as three apexes, in a ternary system phase diagram of a Si3N4-SiO2-LU2O3 system.

Abstract: A high pressure phase spinel type sialon represented by the chemical formula Si6−xAlxOxN8−x (0<x≦4.2), and a high pressure phase spinel type silicon oxynitride represented by the chemical formula Si3+xO2xN4 (═Si3N4.xSiO2, 0<x<1). Methods for their production by instantaneous pressing by means of an impulse wave.

Abstract: A superplastic silicon nitride sintered body which is a sintered body of silicon nitride and which has superplasticity such that when a compression or tensile stress of from 30 to 2000 kg/cm.sup.2 is applied thereto at a temperature within a range of from 1350.degree. to 1650.degree. C., it deforms at a deformation rate of from 10.sup.-4 /sec to 10.sup.-1 /sec.

Abstract: A superplastic silicon carbide sintered body which comprises at least 85 wt % and at most 98 wt % of silicon carbide grains and more than 2 wt % and less than 15 wt % of a grain boundary phase and which has a relative density of at least 95%, wherein the silicon carbide grains have an average grain size of at most 0.3 .mu.m, the amount of grains having grain sizes exceeding 0.5 .mu.m is at most 3 wt %, and the deformation rate of the sintered body is at least 10.sup.-4 /sec under a compression or tensile stress of from 50 to 2,000 kg/cm.sup.2 within a temperature range of from 1,600.degree. to 1,800.degree. C.

Abstract: A high strength and toughness .beta.-silicon nitride sintered body suitable for the material of a variety of structural parts. The sintered body contains .beta.-silicon nitride (Si.sub.3 N.sub.4) in an amount not less than 95% by weight of total silicon nitride; oxygen in a total amount not more than 3% by weight of the sintered body; and columnar grains each of which has a diameter not less than 5 .mu.m and an aspect ratio not less than 5, the columnar grains being in an amount not less than 0.5% by volume of total of raw materials in the sintered body; the sintered body having a bulk density not less than 96% of a theoretical density. Such a sintered body is produced by a method comprising the following steps in the sequence set forth: preparing powder of a starting material including .beta.-silicon nitride in an amount not less than 80% by weight of the starting material; adding oxide of at least one element selected from the group IIIa of the periodic table of elements in an amount ranging from 0.

Abstract: A high strength and toughness .beta.-silicon nitride sintered body suitable for the material of a variety of structural parts. The sintered body contains .beta.-silicon nitride (Si.sub.3 N.sub.4) in an amount not less than 95% by weight of total silicon nitride; oxygen in a total amount not more than 3% by weight of the sintered body; and columnar grains each of which has a diameter not less than 5 .mu.m and an aspect ratio not less than 5, the columnar grains being in an amount not less than 0.5% by volume of total of raw materials in the sintered body; the sintered body having a bulk density not less than 96% of a theoretical density. Such a sintered body is produced by a method comprising the following steps in the sequence set forth: preparing powder of a starting material including .beta.-silicon nitride in an amount not less than 80% by weight of the starting material; adding oxide of at least one element selected from the group IIIa of the periodic table of elements in an amount ranging from 0.

Abstract: An .alpha.-SIALON powder composed essentially of .alpha.-SIALON having the formula M.sub.x (Si,Al).sub.12 (O,N).sub.16 wherein M is at least one element selected from the group consisting of Li, Mg, Ca, Mn, Y and lanthanide metals and O<x.ltoreq.2.

Abstract: A process for producing fine non-oxide powder from an alkoxide selected from the group consisting of a silicon alkoxide and an aluminum alkoxide, which comprises dispersing carbon powder in the alkoxide, hydrolyzing the dispersion, and heating the hydrolyzate mixture thereby obtained, in a nitrogen atmosphere at a temperature of from 1350.degree. C. to 1650.degree. C. for from 30 minutes to 30 hours.

Abstract: A process for producing a translucent .beta.-sialon sintered product, which comprises mixing fine powders of silicon nitride and aluminum nitride having a high purity of at least 99% and a particle size of at most 200 microns and fine powders of aluminum oxide and silicon oxide having a high purity of at least 99% in such a proportion as to form .beta.-sialon of the formula Si.sub.6-z Al.sub.z O.sub.z N.sub.8-z where z is from 1 to 4.2, and hot-pressing the mixture in a nitrogen atmosphere at a temperature of from 1500.degree. to 1850.degree. C. under pressure of from 10 to 1500 kg/cm.sup.2.

Abstract: SIALON sintered product having the formulaSi.sub.6-z Al.sub.z O.sub.z N.sub.8-z(z is 0 to 4.2) is produced by sintering a molded product of the starting materials for SIALON in the condition of covering the surface of said molded product with a mixed powder of Si.sub.3 N.sub.4 and SiO.sub.2 as main components in nitrogen gas atmosphere.