Novel rare-earth doped fluorides and process for preparing

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The invention is directed a composition represented by the chemical formula EuxA1-xF2+x-2yOy wherein A is alkaline earth, 0.002 ≤ x ≤ 0.20, and 0 ≤y ≤x; the composition exhibiting a luminescence spectrum characterized by peaks at 592 ± 2 nm and 627 ± 2 nm, wherein the ratio of the peak intensity at 592 ± 2 nm to that at 627 ± 2 nm is at least 5% larger than the corresponding peak intensity ratio at the same wavelengths of a first corresponding reference composition with the same value of x that has not been exposed to a temperature above 100°C, and wherein said ratio of the peak intensity at 592 ± 2 nm to that at 627 ± 2 nm is at least 5% smaller than the corresponding peak intensity ratio at the same wavelengths of a second corresponding reference composition with the same value of x that has been subject to heating to 900°C for 6 hours.