Abstract: An actuator of the present invention is composed of a monomorph-type piezoelectric ceramic. The monomorph-type piezoelectric ceramic is a BaTiO.sub.3 -based ceramic, a PZT based ceramic having Nb, Sb, La, Mn, Nd and Bi, BaTiO.sub.3 --SrTiO.sub.3 -based ceramic containing SrTiO.sub.3 by 20 to 35 mole %, K(Nb, Ta)O.sub.3 -based ceramic, or a ceramic represented by a general formula: [Pb, (A.sub.1/2 B.sub.1/2)](Zr.sub.1-n, Cn)O.sub.3 where A is a monovalent element such as Li, Na, K, Rb, Cs or the like, B is a trivalent element such as Bi, La, Y, Sb, Ga or the like, A and B being both replaceable solid-meltable elements for Pb, C is an element such as Ti, Sn or the like that is a replaceable solid-meltable element for Zr, and n is from 0 to 0.8.

Abstract: A zirconia type sintered body consisting essentially of 50 to 98% by weight of zirconia (ZrO.sub.2) containing 1.5 to 5 mole % of yttria (Y.sub.2 O.sub.3) and 50 to 2% by weight of alumina (Al.sub.2 O.sub.3), spinal (MgAl.sub.2 O.sub.4) or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2), and having a three-point bending strength of at least 1700 MPa is provided. This sintered body is prepared by a process wherein a powdery composition consisting essentially of 50 to 98% by weight of (a1) a powder of zirconia containing 1.5 to 5 mole % of yttria or (a2) a mixture comprising 1.5 to 5 mole % of yttria powder and 95 to 98.5 mole % of a zirconia powder and 2 to 50% by weight of (b) a powder of an alumina type oxide selected from alumina, and alumina-magnesia type oxide, an alumina-silica type oxide, a mixture of alumina and magnesia and a mixture of alumina and silica is subjected to a hot isotactic pressing treatment under a pressure of at least 50 MPa at temperature of 1300.degree. C. to 1700.degree. C.

Abstract: Disclosed is a process for the preparation of high .alpha.-type silicon nitride powder, wherein a nitrogen-containing silane compound and/or amorphous silicon nitride is crystallized to form crystalline silicon nitride. In this process, crystalline silicon nitride having a particle size not larger than 0.05 .mu.m is incorporated in an amount of at least 0.1% by weight into the nitrogen-containing silane compound and/or amorphous silicon nitride, the mixture is formed into a power or molded body having a powder bulk density of at least 0.1 g/cm.sup.3 as silicon, and the powder or molded body is heated to 1,350.degree. to 1,700.degree. C. while controlling the temperature-elevating rate to at least 15.degree. C./min throughout the temperature range of from 1,200.degree. to 1,350.degree. C. The resulting high .alpha.-type silicon nitride is composed of a fine granular crystal and the does not contain a needle crystal or columnar crystal.

Abstract: A high .alpha.-type silicon nitride powder is prepared by thermally decomposing a mixture of a crystalline silicon nitride powder having an oxygen content of at least 1.0% by weight and a nitrogen-containing silane compound.

Abstract: A sintered product of zirconia comprising ZrO.sub.2 and CeO.sub.2 in a molar ratio of CeO.sub.2 /ZrO.sub.2 of 8/92-30/70, and consisting of a crystal phase which is a mixed phase consisting essentially of a tetragonal phase and a cubic phase, or which is a phase consisting essentially of a tetragonal phase, has a high mechanical strength and a high rupture toughness, and is applicable as the constituting materials of tools for machining and cutting, various kinds of dies and nozzles, parts for sliding and other industrial materials.

Abstract: A high strength metal working tool such as cutting tools and dies made of a zirconia-base sintered material comprising 50 to 98 weight percent of zirconia (ZrO.sub.2) containing 1.5 to 5 mol percent of yttira (Y.sub.2 O.sub.3) and 50 to 2 weight percent of alumina (Al.sub.2 O.sub.3) and/or spinel (MgAl.sub.2 O.sub.4) and having a three point bending strength of not less than 1700 MPa.

Abstract: A silicon nitride powder having an enhanced sintering activity is prepared by heating a mixture of a nitrogen-containing silane compound and a sintering aid in a non-oxidizing atmosphere.

Abstract: A zirconia type sintered body consisting essentially of 50 to 98% by weight of zirconia (ZrO.sub.2) containing 1.5 to 5 mole % of yttria (Y.sub.2 O.sub.3) and 50 to 2% by weight of alumina (Al.sub.2 O.sub.3), spinal (MgAl.sub.2 O.sub.4) or mullite (3Al.sub.2 O.sub.3.2SiO.sub.2), and having a three-point bending strength of at least 1700 MPa is provided. This sintered body is prepared by a process wherein a powdery composition consisting essentially of 50 to 98% by weight of (a1) a powder of zirconia containing 1.5 to 5 mole % of yttria or (a2) a mixture comprising 1.5 to 5 mole % of a yttria powder and 95 to 98.5 mole % of a zirconia powder and 2 to 50% by weight of (b) a powder of an alumina type oxide selected from alumina, an alumina-magnesia type oxide, an alumina-silica type oxide, a mixture of alumina and magnesia and a mixture of alumina and silica is subjected to a hot isotactic pressing treatment under a pressure of at lesast 50 MPa at temperature of 1300.degree. C. to 1700.degree. C.

Abstract: A method of manufacturing highly purified silicon nitride including the steps of preparing a nitrogen-containing silane selected from the group consisting of tetra-amide-monosilane and silicon imide, and heat-treating the prepared nitrogen-containing silane in the presence of ammonia in an inner atmosphere at a temperature above 400.degree. C. for a period of at least two hours to obtain silicon nitride, and cooling and collecting the silicon nitride thus formed. The step of preparing the nitrogen-containing silane comprises continuously reacting gaseous silicon tetra-chloride with gaseous ammonia in an inner atmosphere at a temperature of from -30.degree. to 70.degree. C. to produce the nitrogen-containing silane as a product and collecting the product. The resultant silicon nitride so produced has a chlorine content of less than 0.05 weight percent and a nitrogen content of over 38 weight percent.

Abstract: High-purity .alpha.-type silicon nitride comprised of a granular crystal having an .alpha.-phase content of at least 95%, a nitrogen content of at least 38% by weight and an average particle size of not larger than 3 .mu.m is provided. This high-purity .alpha.-type silicon nitride is prepared by heating a nitrogen-containing silane compound at a temperature of at least about 1,300.degree. C. in a heating furnace comprised of a material containing a metal having a melting point exceeding 1,600.degree. C. and capable of being bonded with oxygen at the heating temperature.

Abstract: Titanium carbonitride of a high purity and in a fine powder form can be produced by maintaining a mixture of titanium halide and carbon at a temperature of from 700.degree. C. to 1,800.degree. C. in the presence of a reducing substance, such as aluminum or an aluminum-titanium alloy, in a nitrogen-containing gaseous atmosphere.