Abstract: The inventive composition, according to a first embodiment, consists essentially of a cerium oxide and a zirconium oxide in an atomic ratio Ce/Zr of at least 1. According to a second embodiment, said composition is based on cerium oxide, zirconium oxide with an atomic ratio Ce/Zr of at least 1 and at least one rare earth oxide other than cerium. After calcination at 1100° C., said composition has a specific surface of at least 9 m2/g in the second embodiment. The inventive composition can be used as a catalyst especially for the treatment of waste gases from internal combustion engines.

Abstract: The inventive composition, according to a first embodiment, consists essentially of a cerium oxide and a zirconium oxide in an atomic ratio Ce/Zr of at least 1. According to a second embodiment, said composition is based on cerium oxide, zirconium oxide with an atomic ratio Ce/Zr of at least 1 and at least one rare earth oxide other than cerium. After calcination at 1100° C., said composition has a specific surface of at least 9 m2/g in the second embodiment. The inventive composition can be used as a catalyst especially for the treatment of waste gases from internal combustion engines.

Abstract: The invention concerns a colloidal dispersion of a vanadate or a phosphovanadate of at least a rare earth comprising either a complex-forming agent having a pK higher than 2.5, or an anion of a monovalent acid, soluble in water and having a pKa ranging between 2.5 and 5. The dispersion is obtained by contacting a colloidal dispersion or a dispersion of initial complexes comprising at least a rare earth compound and at least a complex-forming agent or an anion of said monovalent acid and whereof the pH has been adjusted to a value of at least 7, with vanadate ions, then, in adjusting the pH of the resulting medium to a value of at least 9 and heating.

Abstract: The invention relates to alkaline-earth or rare-earth metal aluminate precursor compounds, to their method of preparation and to their use in particular as phosphor precursors. These alkaline-earth or rare-earth metal aluminate precursor compounds are essentially crystallized in the form of a transition alumina and in the form of substantially spherical and chemically homogeneous particles including pores whose mean diameter is of at least 10 nm.

Abstract: The invention concerns a colloidal dispersion of a phosphate of a rare earth and a process for its preparation. The dispersion is characterized in that it comprises anisotropic and disaggregated or disaggregatable particles of a phosphate of at least one rare earth and an anion of a monobasic acid, soluble in water and with a pKa of at least 2.5. It is prepared by a process in which a solution of a salt of at least one rare earth is mixed with phosphate ions while controlling the pH of the reaction medium to a value in the range 4 to 9 and in the presence of a monobasic acid, soluble in water and with a pKa of at least 2.5; the mixture obtained optionally undergoes a maturing step; the precipitate is then separated from the reaction medium; and said precipitate is then dispersed in water.

Abstract: The invention concerns an aqueous colloidal dispersion of isotropic particles of a phosphate of at least one rare earth and is characterized in that it comprises either a complexing agent with a pK (cologarithm of the dissociation constant of the complex formed by the complexing agent and said rare earth) of more than 2.5; or an anion of a monobasic acid, soluble in water and with a pKa in the range 2.5 to 5; or said complexing agent and/or said anion of a monobasic acid. In the case of cerium and lanthanum, the mean particle size is at most 20 nm. The dispersions can have a degree of colloid agglomeration of less than 40%.This dispersion can be prepared by forming an aqueous mixture comprising at least one rare earth salt and the complexing agent or monobasic acid anion; by adding a base then phosphate ions to the mixture formed; and heating the mixture obtained. A precipitate is obtained that is re-dispersed in water.

Abstract: The invention concerns a light transforming material, in particular for greenhouse walls, comprising as additive a barium and magnesium silicate of formula Ba3(1-x)Eu3xMg1-yMnySi2O8, wherein 0<x?0.3 and 0<y?0.3and 0<y=0.3. The material is capable of transforming solar energy of UV range into a red light. The material can also be used in paints and cosmetics.

Abstract: The invention concerns a process for preparing an oxide based on zirconium and titanium in which a liquid medium containing a zirconium compound and a titanium compound is formed; said medium is then heated; the precipitate obtained from the end of the preceding step is recovered and optionally, said precipitate is calcined. The invention also concerns an oxide based on zirconium and titanium. Said oxide can comprise in the range 30% to 40% by weight of titanium oxide and in this case it has a pure ZrTiO4 type structure or a mixture of phases of structure type ZrTiO4 and structure type anatase. Said oxide can also comprise in the range 10% to 20% by weight of titanium oxide and it then has a specific surface area of at least 40 m2/g after calcining for 5 hours at 800° C.

Abstract: The invention relates to an aqueous paint composition, particularly a lacquer or a varnish and an aqueous colloidal dispersion of cerium. Said dispersion has a pH of at least 7 and comprises an organic acid with at least three acid functions of which the third pK is at most 10 or a salt of said acid with ammonia or an amine. Said composition has an improved water content and mechanical properties which improve throughout the life thereof or the duration of the presence thereof on the substrate for protection.

Abstract: The colloidal dispersion of the invention is characterized in that it comprises an organic phase; particles of an iron compound in its amorphous form; and at least one amphiphilic agent. It is prepared by a process in which either an iron salt in the presence of an iron complexing agent or an iron complex is reacted with a base, maintaining the pH of the reaction medium at a value of at most 8 to obtain a precipitate, the iron complexing agent being selected from hydrosoluble carboxylic acids with a complexing constant K such that the pK is at least 3 and the iron complex being selected from the products of reacting iron salts with said acids; then the precipitate obtained or a suspension containing said precipitate is brought into contact with an organic phase in the presence of an amphiphilic agent to obtain the dispersion in an organic phase. The dispersion of the invention can be used as a combustion additive in liquid fuel or motor fuel.

Abstract: The invention concerns a process for preparing an oxide based on zirconium and titanium in which a liquid medium containing a zirconium compound and a titanium compound is formed; said medium is then heated; the precipitate obtained from the end of the preceding step is recovered and optionally, said precipitate is calcined. The invention also concerns an oxide based on zirconium and titanium. Said oxide can comprise in the range 30% to 40% by weight of titanium oxide and in this case it has a pure ZrTiO4 type structure or a mixture of phases of structure type ZrTiO4 and structure type anatase. Said oxide can also comprise in the range 10% to 20% by weight of titanium oxide and it then has a specific surface area of at least 40 m2/g after calcining for 5 hours at 800° C.

Abstract: The invention concerns a process for preparing rare earth borates, and the use of these borates in luminescence. The preparation process is characterized in that it comprises the following steps mixing boric acid and a rare earth salt; a reacting the mixture obtained with a carbonate or a bicarbonate; a calcining the precipitate obtained.

Abstract: The invention concerns a colloidal dispersion of a phosphate of a rare earth and a process for its preparation. The dispersion is characterized in that it comprises anisotropic and disaggregated or disaggregatable particles of a phosphate of at least one rare earth and an anion of a monobasic acid, soluble in water and with a pKa of at least 2.5. It is prepared by a process in which a solution of a salt of at least one rare earth is mixed with phosphate ions while controlling the pH of the reaction medium to a value in the range 4 to 9 and in the presence of a monobasic acid, soluble in water and with a pKa of at least 2.5; the mixture obtained optionally undergoes a maturing step; the precipitate is then separated from the reaction medium; and said precipitate is then dispersed in water.

Abstract: The inventive composition, according to a first embodiment, consists essentially of a cerium oxide and a zirconium oxide. According to a second embodiment, said composition is based on cerium oxide, zirconium oxide and at least one rare earth oxide other than cerium. After a first 4-hour period of calcination at 900 .C followed by a second 10-hour period of at 1000 .C, the specific surface variation thereof is 20% maximum in the first embodiment and 15% maximum in the second embodiment. The inventive composition can be used as a catalyst, i.e. in the treatment of waste gases from internal combustion engines.

Abstract: The invention relates to a compound based on at least one element A chosen from alkaline-earth metals, on at least one element B chosen from aluminium, gallium and indium, on sulphur and on a dopant capable of giving the compound luminescence properties, which is characterized in that it is in the form of a mixture of predominantly an AB2S4-type crystallographic phase and a B2S3-type crystallographic phase. This compound is prepared by a method in which a solution or suspension comprising salts or sols of the elements A, B and of the dopant is formed in a proportion such that the B/(A+dopant) atomic ratio is at least 2.06; the solution or suspension is spray-dried; the product thus obtained is sulphurized. This compound may be used as a phosphor, especially in cathodoluminescence.