The present invention is a method of producing a lanthanum carbonate hydroxide or lanthanum oxycarbonate which has improved properties. The method involves the use of a water soluble lanthanum and a water soluble non-alkali metal carbonate or bicarbonate. The resulting material can be used as a phosphate binder individually or for treating patients with hyperphosphatemia.

The present invention is a method of producing a lanthanum carbonate hydroxide or lanthanum oxycarbonate which has improved properties. The method involves the use of a water soluble lanthanum and a water soluble non-alkali metal carbonate or bicarbonate. The resulting material can be used as a phosphate binder individually or for treating patients with hyperphosphatemia.

Rare earth compound particles are prepared by a step of heating an aqueous solution containing rare earth metal ions and urea to form a rare earth compound by a reaction of a hydrolysis product of urea, and the rare earth metal ions. In the heating step, heating the aqueous solution into which an acetylene glycol-ethylene oxide adduct is added.

The present invention provides a novel anion conductor which comprises a layered metal hydroxide and can be used as an alkaline electrolyte film for use in a fuel cell or the like. An anion conductor characterized by comprising a molded product of a layered metal hydroxide represented by formula (1): [M.sub.x(OH).sub.y(A).sub.(αx-y)/z-nH.sub.2O] (wherein M represents a metal that can serve as a bivalent or trivalent cation; α represents the number of valency of the metal M, A represents an atom or an atomic group that can serve as an anion, and z represents the number of valency of the anion A, wherein, when (αx-y)/z is 2 or greater, A's may be different types of anions which can serve as anions having the same valencies as each other, or may be anions having different valencies from each other; and n represents the average number of molecules of interlayer water contained per one repeating unit). The anion conductor according to the present invention is composed of an inorganic material, and therefore has excellent heat resistance and physical strength and can be operated for a longer period at a higher temperature compared with the conventional ones when used as an anion conductor for a fuel cell, an air cell or the like.

A method for producing rare earth carbonate fine particles, including, forming a reaction solution in which an alkyldimethylamine oxide compound having a structure represented by the following formula (1) or a methylmorpholine oxide compound is added to an aqueous solution containing rare earth ion and an excess amount of urea with respect to the rare earth ion, such that the compound is added in an addition amount of 10 to 200 mol % relative to the rare earth ion, and subjecting the reaction solution to hydrothermal treatment to produce rare earth carbonate fine particles. This provides a method for producing rare earth carbonate fine particles of submicron or less and having excellent dispersibility.

##STR00001##

wherein R represents an alkyl group of C1 to C14.

A method for producing rare earth carbonate fine particles, including, forming a reaction solution in which an alkyldimethylamine oxide compound having a structure represented by the following formula (1) or a methylmorpholine oxide compound is added to an aqueous solution containing rare earth ion and an excess amount of urea with respect to the rare earth ion, such that the compound is added in an addition amount of 10 to 200 mol % relative to the rare earth ion, and subjecting the reaction solution to hydrothermal treatment to produce rare earth carbonate fine particles. This provides a method for producing rare earth carbonate fine particles of submicron or less and having excellent dispersibility.

##STR00001##

wherein R represents an alkyl group of C1 to C14.

The present invention provides a method for obtaining a specifically-shaped crystal (specifically, spherocrystal) of a compound with good reproducibility. This method for producing a specifically-shaped crystal (specifically spherocrystal) of a compound comprises: (1) a step for preparing a supersaturated solution of a compound having a degree of supersaturation equal to or higher than a critical degree of supersaturation; and (2) a step for precipitating a specifically-shaped crystal (specifically spherocrystal) of a compound from the supersaturated solution.

The present invention provides a method for obtaining a specifically-shaped crystal (specifically, spherocrystal) of a compound with good reproducibility. This method for producing a specifically-shaped crystal (specifically spherocrystal) of a compound comprises: (1) a step for preparing a supersaturated solution of a compound having a degree of supersaturation equal to or higher than a critical degree of supersaturation; and (2) a step for precipitating a specifically-shaped crystal (specifically spherocrystal) of a compound from the supersaturated solution.

An aqueous solution containing ions of one or more rare earth elements selected from the group consisting of Y, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, hydrogen peroxide, urea, and polyvinylpyrrolidone is heated at a temperature of 80° C. or higher and equal to or lower than a boiling point of the aqueous solution to produce particles of a rare earth compound under a reaction between a hydrolysis product of urea and the ions of the rare earth elements. Furthermore, the particles of the rare earth compound are solid-liquid separated from the aqueous solution, and the obtained solid content is baked at a temperature of 600° C. or higher in an atmosphere containing oxygen to produce rare earth oxide particles.

An aqueous solution containing ions of one or more rare earth elements selected from the group consisting of Y, Nd, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, hydrogen peroxide, urea, and polyvinylpyrrolidone is heated at a temperature of 80° C. or higher and equal to or lower than a boiling point of the aqueous solution to produce particles of a rare earth compound under a reaction between a hydrolysis product of urea and the ions of the rare earth elements. Furthermore, the particles of the rare earth compound are solid-liquid separated from the aqueous solution, and the obtained solid content is baked at a temperature of 600° C. or higher in an atmosphere containing oxygen to produce rare earth oxide particles.