Abstract: Rare earth-containing compound particles of polyhedral shape having an average particle diameter of 3-100 &mgr;m, a dispersion index of up to 0.5, and an aspect ratio of up to 2 can be thermally sprayed to form an adherent coating, despite the high melting point of the rare earth-containing compound. A sprayed component having the particles spray coated on a substrate surface is also provided.

Abstract: A conductive filler in the form of non-conductive particles coated with plural layers of metal plating is provided wherein the lower layer is of copper or copper alloy plating, and the uppermost layer is of gold plating. The conductive powder has a high conductivity, improved durability, especially oxidation resistance, and a relatively low specific gravity.

Abstract: Disclosed is a method for the preparation of a high-quality sintered body of a rare earth oxide or a composite oxide of a rare earth oxide and an adjuvant oxide such as aluminum oxide. The method comprises shaping a rare earth oxide powder characterized by specified particle diameter distribution values of D50 and D90 and a specified specific surface area or a powder blend of the rare earth oxide and adjuvant oxide into a powder compact and subjecting the powder compact to a sintering heat treatment at a specified sintering temperature by increasing and decreasing the temperature up to and from the sintering temperature each at a rate not exceeding a specified upper limit.

Abstract: Disclosed is an improvement in the method for the preparation of a rare earth oxide powder particularly suitable as a base material of luminescence phosphors. The improvement comprises, in a method comprising the steps of mixing aqueous solutions of a rare earth salt and oxalic acid to precipitate the rare earth oxalate, collecting the precipitates by filtration, drying the precipitates and calcining the dried precipitates, conducting the oxalate-precipitating reaction at a temperature at 15° C. or lower and freezing the wet precipitates at −25° C. or lower prior to vacuum drying to give dried particles of the rare earth oxalate containing 20% by weight or less of water including the water of crystallization. The particles of the thus obtained rare earth oxide powder are characterized by the small pore volume and average crystallite diameter.

Abstract: A conductive filler is provided in the form of non-conductive particles which are surface coated with a plating layer of copper, copper alloy, nickel or nickel alloy, which is, in turn, coated with an electroplating layer of gold, gold alloy, silver or silver alloy. The conductive powder has a high conductivity, durability, especially oxidation resistance, and a relatively low specific gravity.

Abstract: Disclosed is a method for the preparation of a high-quality sintered body of a rare earth oxide or a composite oxide of a rare earth oxide and an adjuvant oxide such as aluminum oxide. The method comprises shaping a rare earth oxide powder characterized by specified particle diameter distribution values of D50 and D90 and a specified specific surface area or a powder blend of the rare earth oxide and adjuvant oxide into a powder compact and subjecting the powder compact to a sintering heat treatment at a specified sintering temperature by increasing and decreasing the temperature up to and from the sintering temperature each at a rate not exceeding a specified upper limit.

Abstract: A conductive filler in the form of non-conductive particles coated with plural layers of metal plating is provided wherein the lower layer is of copper or copper alloy plating, and the uppermost layer is of gold plating. The conductive powder has a high conductivity, improved durability, especially oxidation resistance, and a relatively low specific gravity.

Abstract: Disclosed is a method for the preparation of particles of a rare earth ammonium double oxalate by mixing a first aqueous solution of ammonium oxalate and a second aqueous solution of a water-soluble rare earth salt. The double oxalate particles have a polyhedral particle configuration with a uniform particle size distribution, from which a rare earth oxide powder of a polyhedral particle configuration with good flowability can be obtained by calcination, when the first and second aqueous solutions are prepared under exact control of the concentrations of the respective ionic species and the aqueous slurry containing the precipitates of the double oxalate is subjected to an aging treatment during which changes take place in the particle morphology and in the crystallographic structure of the double oxalate particles.

Abstract: Proposed is a method for the preparation of a rare earth oxide powder consisting of particles having a globular particle configuration to be suitable as a base material of phosphors. The method comprises the steps of mixing an aqueous solution of a rare earth salt and an aqueous alkaline solution, e.g., ammonia water, to precipitate a rare earth hydroxide which is collected, washed with water and calcined to be converted into the oxide powder. Characteristically, the precipitation reaction of the rare earth hydroxide is carried out in the presence of a nitrogen-containing chelating agent such as triethanolamine in the aqueous medium in a controlled amount.

Abstract: An improved method is proposed for the preparation of a powder of rare earth oxide of which the particles have a predominantly polyhedral configuration with a relatively large particle size to be suitable, for example, as a host of phosphors. The method comprises the steps of (a) precipitating a rare earth ammonium oxalate by the admixture of an aqueous solution of a rare earth salt and ammonium oxalate, (b) separating the precipitates from the aqueous medium, (c) washing the same with deionized water to be freed from electrolytes, (d) dispersing and keeping the precipitates in a hot water bath at 50.degree. C. or higher for at least 15 minutes, (e) collecting the precipitates and (f) calcining the precipitates of the rare earth ammonium oxalate into oxide. It is essential that the steps (a) to (c) are conducted at a temperature of 40.degree. C. or below or, preferably, 30.degree. C. or below.