Luminescent mixed borates based on rare earths
AssigneeCentre National de la Recherche Scientifique (CNRS)
InventorsClaude E. Fouassier, Wen T. Fu, Paul Hagenmuller
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Abstract
Monophase crystalline mixed borates having the formula: M(II).sub.1-x Eu(II).sub.x M(III).sub.p Eu(III).sub.q Tb(III).sub.r B.sub.9 O.sub.16 wherein M(II) is at least one bivalent metal selected among barium, strontium, lead and calcium, it being understood that, in a given mixed borate, the lead and the calcium, together represent not more than 20% by moles based on the total number of moles of metals M(II); M(III) is a metal selected among lanthanum, gadolinium, yttrium, serium, lutetium and bismuth; x is a number higher or equal to zero and smaller than or equal to 0.2; p, q and r is different from zero; and the sum p+q+r equals 1; preparation method and luminescent composition containing them.
Claims12
A luminescent mixed borate consisting of a monophase crystalline product having the formula
- M(Il).sub.1-x Eu(II).sub.x M(III).sub.p Eu(III).sub.q Tb(III).sub.r B.sub.9 O.sub.16 (I)
- wherein
- M(II) represents at least one divalent metal selected from the group consisting of barium, strontium, lead and calcium, with the proviso that in said mixed borate, the amount of lead and calcium taken together does not represent more than 20 molar percent relative to the total number of moles of said M(II) metal,
- M(III) represents a metal selected from the group consisting of lanthanum, gadolinium, yttrium, cerium, lutetium and bismuth,
- x is a number greater than or equal to 0 and lower than or equal to 0.2,
- p, q and r each represent a number ranging from 0 to 1, with the proviso that for a given borate at least one of the x, q and r numbers is other than 0 and the sum or p+q+r is equal to 1, and wherein said mixed borate is selected from the group consisting of (1) that for which q equals 0 and (2) that for which x equals r equals 0 and when q=r=0, M(II) is barium and M(III) is gadolinium, the mixed borate has a luminescence spectrum substantially as depicted in FIG. 3.
A luminescent composition comprising at least one mixed borate consisting of a monophase crystalline product having the formula
- M(II).sub.1-x Eu(II).sub.x M(III).sub.p Eu(III).sub.q Tb(III).sub.r B.sub.9 O.sub.16 (I)
- wherein
- M(II) represents at least one divalent metal selected from the group consisting of barium, strontium, lead and calcium, with the proviso that in said mixed borate, the amount of lead and calcium taken together does not represent more than 20 molar percent relative to the total number of moles of said M(II) metal,
- M(III) represents a metal selected from the group consisting of of lanthanum, gadolinium, yttrium, cerium, lutetium and bismuth,
- x is a number greater than or equal to 0 and lower than or equal to 0.2,
- p, q and r each represent a number ranging from 0 to 1, with the proviso that for a given borate at least one of the x, q and r numbers is other than 0 and the sum of p+q+r is equal to 1, and wherein said mixed borate is selected from the group consisting of (1) that for which q equals 0 and (2) that for which x equals r equals 0 and when q=r=0, M(II) is barium and M(III) is gadolinium, the mixed borate has a luminescence spectrum substantially as depicted in FIG. 3, and an excess of B.sub.2 O.sub.3 and/or an oxide of M(II) metal wherein M(II) is defined above, said excess being 20 mole percent of said B.sub.2 O.sub.3 and/or 50 mole percent of said oxide of M(II) metal relative to said at least one mixed borate.
Dependencies are inferred from the claim text.