STRUCTURAL AND OPTICAL-PROPERTIES OF THE SYSTEM (SR, BA, EU)(5)(PO4)(3)CL

Polycrystalline materials prepared by solid state reaction have the co mposition Sr5-x-yBaxEuy(PO4)(3)Cl with 0 less than or equal to x less than or equal to 4.99 and 0 less than or equal to y less than or equal to 0.05. The crystal structure of the mixed crystals, optical propert ies at room temperature, and the emission spectra at liquid nitrogen t emperature are studied. Rietveld profile refinement procedures are use d. The materials crystallize hexagonal with the space group P6(3)/m. T he alkaline earth ions occupy two different positions of the unit cell . With rising barium content in the polycrystalline materials the latt ice constants ao and co increase and a second emission band appears an d above x = 3.42 disappears. The luminescence of the samples arises fr om transitions between 4f(6)5d and 4f(7) configurations of the Eu2+ io n.