Rhodia Operations

Thierry Le-Mercier

Serena Carella

Valérie Buissette

Paolo Toniolo

Laurent Thiers

Franck Aurissergues

Yvan Montardi

Olivier Le-Roux

Lauriane D'ALENÇON

The silicate of magnesium and of barium, strontium or calcium of the invention is characterized in that it is in the form of a suspension of solid crystallized particles in a liquid phase, said particles having a mean size between 0.1 &#x3bc;m and 1 &#x3bc;m. It is prepared by spray-drying a liquid mixture comprising compounds of magnesium, of silicium and of at least one first element chosen from barium, strontium and calcium, by submitting the dried mixture to a first calcination in air and to a second calcination in a reducing atmosphere and by wet milling the calcined mixture.

Suspension of a magnesium silicate, method for making same and use thereof as a phosphor

Phosphate particulates of at least one rare-earth metal (Ln), with Ln being at least one rare-earth metal selected from among cerium and terbium and optionally lanthanum are in the form of a suspension in a liquid phase of primary isotropic monocrystalline monazite particles having an average size of at least 25 nm and agglomerated into secondary particles having an average size of at most 400 nm; useful luminophores are produced from such phosphate particulates.

Suspensions of phosphates of at least one rare earth element selected from among cerium and terbium and optionally lanthanum and luminophores produced therefrom

The phosphor of the invention is based on a lanthunum cerium terbium phosphate, and it is characterized in that the phosphate consists of particles having a mean size of at most 4 &#x3bc;m, in that it has a lithium content of at most 30 ppm, a boton content of at most 30 ppm and in that it has a variation of brightness between the brightness measured on the phosphor at 25&#xb0; C. and that measured on the same phosphor at 200&#xb0; C. of at most 4%.

Phosphor based on a lanthanum cerium terbium phosphate with stabilized brightness, preparation process and use in a luminescent device

A novel type of green luminophore containing mixed rare-earth phosphates is produced from precursor particles having a mean diameter ranging from 1.5 to 15 microns; such particles have an inorganic core and a shell of a mixed lanthanum and/or cerium phosphate, optionally doped with terbium, evenly covering the inorganic core with a thickness greater than or equal to 300 nm.

Luminophores and core-shell luminophore precursors

A composition comprising an inorganic core and an aluminate shell is described. The aluminate can have the formula (1):(CeTb)MgAlO&#x2003;&#x2003;(1),where a, b, x and y comply with the relations a+b=1&#x2212;0.2&#x2266;x&#x2266;+0.2 and &#x2212;0.2&#x2266;y&#x2266;+0.2, wherein the shell uniformly covers the inorganic core over a thickness of no less than 300 nm. A phosphor is also described that can be obtained by calcinating the composition at a temperature of at least 1200&#xb0; C.

Composition containing a core-shell aluminate, phosphor obtained from said composition, and preparation methods

A composition including an inorganic core and a europium and yttrium oxide or gadolinium shell uniformly covering the inorganic core at a thickness greater than or equal to 300 nm is described. A phosphor including the composition is also described. In addition a process of forming the composition by: forming a suspension including the inorganic core with pH of 8 to 11; adding a solution including a europium salt and yttrium or gadolinium salt to the suspension and maintaining the pH of the reaction medium at a constant value; and separating the formed solid and calcining the same to a temperature of at most 1000&#xb0; C. is described.

Europium, and yttrium oxide or gadolinium oxide core/shell composition, phosphor including said composition, and methods for preparing same

Liquid phase suspensions of substantially monocrystalline rare-earth borate particles, the mean size thereof ranging from 100 to 400 nm, are prepared by roasting a rare earth borocarbonate or hydroxyborocarbonate at a temperature which is sufficient for forming a borate and obtaining a product whose specific surface area is equal to or greater than 3 m/g and then wet grinding the roasted product; such borates are useful in the form of luminophors, in particular, as luminescent transparent materials.

Submicron rare-earth borates and preparation/luminoshors thereof

Submicronic barium and magnesium aluminates, useful as phosphors, are in the form of a liquid-phase suspension of substantially monocrystalline particles having an average particle size ranging from 80 to 400 nm; such aluminates are prepared by a process that includes: providing a liquid mixture containing compounds of aluminum and of other elements that are part of the aluminate composition; drying the mixture by atomization; calcining the dried product in a reducing atmosphere and wet-grinding this product.

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Rosny Sous Bois, France

Thierry Le-Mercier