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.