Abstract: An improved material in the form of rare-earth borate, its precursor(s) and a luminophore made thereof is provided. The material is characterizable as comprising spherical, cubic or parallelepipedal particles having an average particle size not more than 10 &mgr;m, over a narrow particle size distribution (dispersion index not greater than 0.8). The material may comprise a rare earth element having that lacks luminescence in combination with a dopant.

Abstract: The present invention relates to the use of a compound based on a thulium-containing lanthanum phosphate as a phosphor in a plasma or X-ray system. This phosphate may furthermore contain gadolinium. The thulium content of the compound, expressed in at % with respect to the lanthanum, is between 0.1 and 10, more particularly between 0.5 and 5. The invention also covers a lanthanum phosphate which is characterized in that it contains thulium and in that it consists of particles having a mean size of between 1 and 20 &mgr;m with a dispersion index of less than 0.6.

Abstract: The present invention relates to a rare-earth borate, to a precursor thereof, to processes for their preparation and to the use of this borate as a luminophore.

Abstract: The present invention provides a process for preparing a rare earth borate by reacting together at least one rare earth salt, boric acid and a base. The process is characterized in that the reaction is carried out using an excess of acid with respect to the stoichiometry and under conditions such that the pH of the reaction medium at the end of the reaction is in the range of 6 to 8. The precipitate formed is then recovered and calcined. The phase purity of the borate obtained is good and it can be used as a luminophore.

Abstract: The present invention relates to a compound based on an alkaline-earth metal, on sulphur and on aluminium, on gallium or indium, to its process of preparation and to its use as luminophore. The compound of the invention corresponds to the formula AB2S4, in which A represents an alkaline-earth metal and B aluminum, gallium, or indium and it is characterized in that it is provided in the form of a powder with a residual oxygen content of not more that 1.5% and composed of particles with a mean size of not more than 10 &mgr;m. This compound is obtained by a process which contains the following stages: a solution or a suspension comprising salts of the elements A and B is formed, the solution or the suspension is dried by atomization and the product obtained in the preceding stages is reacted with carbon disulphide or with a mixture of hydrogen sulphide and or carbon disulphide. The compound of the invention can be used as a luminophore, in particular in cathodoluminescence.

Abstract: The present invention relates to a rare-earth borate, to a precursor thereof, to processes for their preparation and to the use of this borate as a luminophore. The rare-earth borate and the precursor thereof are characterized in that they are in the form of cubic, parallelepipedal or spherical particles and in that they have a dispersion index of not more than 0.8. According to one embodiment of the invention, the borate is a red luminophore. The process for the preparation of the precursor is characterized in that a rare-earth carbonate or hydroxycarbonate is reacted with boric acid, the reaction medium being in the form of an aqueous solution. The borate is obtained by calcination of the precursor.

Abstract: The present invention relates to a compound based on an alkaline-earth metal, on sulphur and on aluminium, on gallium or indium, to its process of preparation and to its use as luminophore. The compound of the invention corresponds to the formula AB2S4, in which A represents an alkaline-earth metal and B aluminum, gallium, or indium and it is characterized in that it is provided in the form of a powder with a residual oxygen content of not more that 1.5% and composed of particles with a mean size of not more than 10 &mgr;m. This compound is obtained by a process which contains the following stages: a solution or a suspension comprising salts of the elements A and B is formed, the solution or the suspension is dried by atomization and the product obtained in the preceding stages is reacted with carbon disulphide or with a mixture of hydrogen sulphide and or carbon disulphide. The compound of the invention can be used as a luminophore, in particular in cathodoluminescence.

Abstract: The invention relates to the use as a luminophor in plasma systems of a compound based on an yttrium, lanthanum, gadolinium or lutecium phosphate doped with at least one rare earth chosen from the group comprising terbium, praseodymium, europium and cerium.

Abstract: The invention relates to the use as a luminophor in plasma systems of a compound based on an yttrium, lanthanum, gadolinium or lutecium phosphate doped with at least one rare earth chosen from the group comprising terbium, praseodymium, europium and cerium.

Abstract: The invention relates to the use as a luminophor in plasma systems of a compound based on an yttrium, lanthanum, gadolinium or lutecium phosphate doped with at least one rare earth chosen from the group comprising terbium, praseodymium, europium and cerium.

Abstract: Colloidal dispersions of solid colloidal particulates in a liquid medium, preferably an aqueous medium, said colloidal particulates comprising a core of cerium oxide at least partially coated with a sheathing layer of titanium oxide, are well suited for the photocatalytic coating of a variety of substrates, e.g., glass or metal, to impart anti-IV, anti-reflecting and/or anti-staining properties thereto.

Abstract: Particulates of a luminophore comprising a doped tantalate of yttrium, lutetium or gadolinium are well suited for low-voltage applications, e.g., for the manufacture of field emission display screens.

Abstract: Needle-shaped solid crystallites of specific LaCeTb phosphates, well suited for the production of green phosphors therefrom, are essentially pure white in color after calcination at 900.degree. C. and have the formula (I):La.sub.x Ce.sub.y Tb.sub.(1-x-y) PO.sub.4 (I)in which x and y are numbers, with x ranging from 0.4 to 0.6 and x+y being greater than 0.8.

Abstract: Novel cerium/lanthanum/terbium (LaCeTb) mixed phosphates, especially useful in luminescence for the production of green phosphors, have the formula (I):La.sub.x Ce.sub.y Tb.sub.1-x-y PO.sub.4in which X ranges from 0.4 to 0.6 and x+y is greater than 0.8, display a lightness (L.sup.*) of greater than 98% after calcination at a temperature above 700.degree. C. in air, and the cerium (IV) and/or terbium (IV) contents of which are very low, even after calcination in air at a temperature above 500.degree. C.

Abstract: Nontoxic yellow/orange pigment compositions, well suited for the coloration of a wide variety of substrates, for example paints, varnishes, plastics, ceramics, etc., comprise a major amount of a zirconium oxide and an additive amount of cerium, praseodymium and/or terbium values, such rare earth values being in the form of the oxides thereof.

Abstract: Novel cerium/lanthanum/terbium (LaCeTb) mixed phosphates, especially useful in luminescence for the production of green phosphors, have the formula (I):La.sub.x Ce.sub.y Tb.sub.1-x-y PO.sub.4in which x ranges from 0.4 to 0.6 and x+y is greater than 0.8, display a lightness (L*) of greater than 98% after calcination at a temperature above 700.degree. C. in air, and the cerium (IV) and/or terbium (IV) contents of which are very low, even after calcination in air at a temperature above 500.degree. C.

Abstract: Needle-shaped solid crystallites of specific LaCeTb phosphates, well suited for the production of green phosphors therefrom, are essentially pure white in color after calcination at 900.degree. C. and have the formula (I):La.sub.x Ce.sub.y Tb.sub.(1-x-y) PO.sub.4 (I)in which x and y are numbers, with x ranging from 0.4 to 0.6 and x+y being greater than 0.8.