Abstract: Provided is a production method of a ?-sialon phosphor that europium ions are solid-solved in ?-sialon, including a mixing process for mixing raw materials of the ?-sialon phosphor; a burning process for burning the raw materials after the mixing process to form the ?-sialon phosphor; a HIP treatment process in which the ?-sialon phosphor after the burning process is subjected to a HIP treatment; an annealing process in which the ?-sialon phosphor after the HIP treatment process is subjected to an annealing treatment; and an acid treatment process in which the ?-sialon phosphor after the annealing process is subjected to an acid treatment. According to the production method of a ?-sialon phosphor, a ?-sialon phosphor excellent in luminescence intensity is obtained.

Abstract: A boron carbide based sintered body having a four-point flexural strength of at least 400 MPa and a fracture toughness of at least 2.8 MPa·m1/2, which has the following two preferred embodiments. (1) A boron carbide-titanium diboride sintered body obtained by sintering a mixed powder of a B4C powder, a TiO2 powder and a C powder while reacting them under a pressurized condition and comprising from 95 to 70 mol % of boron carbide and from 5 to 30 mol % of titanium diboride, wherein the boron carbide has a maximum particle diameter of at most 5 ?m. (2) A boron carbide-chromium diboride sintered body containing from 10 to 25 mol % of CrB2 in B4C, wherein the sintered body has a relative density of at least 90%, boron carbide particles in the sintered body have a maximum particle diameter of at most 100 ?m, and the abundance ratio (area ratio) of boron carbide particles of from 10 to 100 ?m to boron carbide particles having a particle diameter of at most 5 ?m, is from 0.02 to 0.6.

Abstract: A boron carbide based sintered body having a four-point flexural strength of at least 400 MPa and a fracture toughness of at least 2.8 MPa·m1/2, which has the following two preferred embodiments. (1) A boron carbide-titanium diboride sintered body obtained by sintering a mixed powder of a B4C powder, a TiO2 powder and a C powder while reacting them under a pressurized condition and comprising from 95 to 70 mol % of boron carbide and from 5 to 30 mol % of titanium diboride, wherein the boron carbide has a maximum particle diameter of at most 5 ?m. (2) A boron carbide-chromium diboride sintered body containing from 10 to 25 mol % of CrB2 in B4C, wherein the sintered body has a relative density of at least 90%, boron carbide particles in the sintered body have a maximum particle diameter of at most 100 ?m, and the abundance ratio (area ratio) of boron carbide particles of from 10 to 100 ?m to boron carbide particles having a particle diameter of at most 5 ?m, is from 0.02 to 0.6.

Abstract: A boron carbide based sintered body having a four-point flexural strength of at least 400 MPa and a fracture toughness of at least 2.8 MPa·m1/2, which has the following two preferred embodiments. (1) A boron carbide-titanium diboride sintered body obtained by sintering a mixed powder of a B4C powder, a TiO2 powder and a C powder while reacting them under a pressurized condition and comprising from 95 to 70 mol % of boron carbide and from 5 to 30 mol % of titanium diboride, wherein the boron carbide has a maximum particle diameter of at most 5 ?m. (2) A boron carbide-chromium diboride sintered body containing from 10 to 25 mol % of CrB2 in B4C, wherein the sintered body has a relative density of at least 90%, boron carbide particles in the sintered body have a maximum particle diameter of at most 100 ?m, and the abundance ratio (area ratio) of boron carbide particles of from 10 to 100 ?m to boron carbide particles having a particle diameter of at most 5 ?m, is from 0.02 to 0.6.

Abstract: A boron carbide based sintered body having a four-point flexural strength of at least 400 MPa and a fracture toughness of at least 2.8 MPa·m1/2, which has the following two preferred embodiments. (1) A boron carbide-titanium diboride sintered body obtained by sintering a mixed powder of a B4C powder, a TiO2 powder and a C powder while reacting them under a pressurized condition and comprising from 95 to 70 mol % of boron carbide and from 5 to 30 mol % of titanium diboride, wherein the boron carbide has a maximum particle diameter of at most 5 ?m. (2) A boron carbide-chromium diboride sintered body containing from 10 to 25 mol % of CrB2 in B4C, wherein the sintered body has a relative density of at least 90%, boron carbide particles in the sintered body have a maximum particle diameter of at most 100 ?m, and the abundance ratio (area ratio) of boron carbide particles of from 10 to 100 ?m to boron carbide particles having a particle diameter of at most 5 ?m, is from 0.02 to 0.6.

Abstract: A boron carbide based sintered body having a four-point flexural strength of at least 400 MPa and a fracture toughness of at least 2.8 MPa·m1/2, which has the following two preferred embodiments. (1) A boron carbide-titanium diboride sintered body obtained by sintering a mixed powder of a B4C powder, a TiO2 powder and a C powder while reacting them under a pressurized condition and comprising from 95 to 70 mol % of boron carbide and from 5 to 30 mol % of titanium diboride, wherein the boron carbide has a maximum particle diameter of at most 5 ?m. (2) A boron carbide-chromium diboride sintered body containing from 10 to 25 mol % of CrB2 in B4C, wherein the sintered body has a relative density of at least 90%, boron carbide particles in the sintered body have a maximum particle diameter of at most 100 ?m, and the abundance ratio (area ratio) of boron carbide particles of from 10 to 100 ?m to boron carbide particles having a particle diameter of at most 5 ?m, is from 0.02 to 0.6.

Abstract: A boron carbide based sintered body having a four-point flexural strength of at least 400 MPa and a fracture toughness of at least 2.8 MPa·m1/2, which has the following two preferred embodiments. (1) A boron carbide-titanium diboride sintered body obtained by sintering a mixed powder of a B4C powder, a TiO2 powder and a C powder while reacting them under a pressurized condition and comprising from 95 to 70 mol % of boron carbide and from 5 to 30 mol % of titanium diboride, wherein the boron carbide has a maximum particle diameter of at most 5 ?m. (2) A boron carbide-chromium diboride sintered body containing from 10 to 25 mol % of CrB2 in B4C, wherein the sintered body has a relative density of at least 90%, boron carbide particles in the sintered body have a maximum particle diameter of at most 100 ?m, and the abundance ratio (area ratio) of boron carbide particles of from 10 to 100 ?m to boron carbide particles having a particle diameter of at most 5 ?m, is from 0.02 to 0.6.

Abstract: A thermionic cathode structure comprises two parallel thermionic electron emitter elements which are made of a heat resistant and electric conductive inorganic compound. Each of them has one end electrically closed and the other end functioning as a current feeding port.