OPTICAL AND STRUCTURAL INVESTIGATION OF KMGLA(PO4)(2) PHOSPHATE DOPEDWITH EUROPIUM

A new compound KMgLa(PO4)(2), isotypic with monoclinic LaPO4, is repor ted. Its cell parameters have been determined from X-ray powder diffra ction data. Crystallization occurs in the monoclinic space group P2(1) /n (No. 14) with a = 6.839(3) Angstrom, b = 7.066(1) Angstrom, c = 6.5 23(3) Angstrom, beta = 103.42(4)degrees, and Z = 2. It was found that the KMgLa(PO4)(2) phase was isostructural with monoclinic LaPO4. The d ifference between them was that half of the La atoms in LaPO4 were cou plingly substituted with the same amount of Mg and K atoms. This isomo rphous substitution was confirmed by IR and Eu3+-doped excitation and emission spectra and by elemental analysis of single crystals. The spe ctroscopic data were compared with those of LaPO4:Eu3+. (C) 1995 Acade mic Press, Inc.