Influence of cation substitution on the crystal structure and luminescent properties in apatite structural Ba4.97−xSrx(PO4)3Cl:0.03Eu2+ phosphors

A series of apatite isostructural Ba4.97−xSrx(PO4)3Cl:Eu2+(x = 0, 0.5, 1.0, 1.5, 2.0) phosphor were synthesized by the high temperature solid-state reaction method. A red shift of the emission peak located in the blue region from 439 to 462 nm was observed with the continuous introduction of Sr2+ into the crystal lattice. A distortion of the inner EuOn polyhedrons was caused due to Ba/Sr ions substituting for Ba ions forming EuOn-Ba/Sr emitting blocks. The crystal field strength surrounding Eu2+ was thus increased, finally resulting in tunable PL properties.144