Luminescence and site occupancy of Ce{sup 3+} in Ba{sub 2}Ca(BO{sub 3}){sub 2}

The phosphors of Ce{sup 3+} activated Ba{sub 2}Ca(BO{sub 3}){sub 2} with chemical formulas Ba{sub 2(1-x)}Ce{sub x}Na{sub x}Ca(BO{sub 3}){sub 2} and Ba{sub 2}Ca{sub 1-2x}Ce{sub x}Na{sub x}(BO{sub 3}){sub 2} were prepared. The luminescence properties have been investigated under vacuum ultraviolet UV and x-ray excitation. Though the point defects Ce{sub Ba{sup {center_dot}}} and Na{sub Ba{sup '}} are expected to occur in samples Ba{sub 2(1-x)}Ce{sub x}Na{sub x}Ca(BO{sub 3}){sub 2}, and Ce{sub Ca{sup {center_dot}}} and Na{sub Ca{sup '}} are expected to appear in samples Ba{sub 2}Ca{sub 1-2x}Ce{sub x}Na{sub x}(BO{sub 3}){sub 2} according to the formulas of the compounds, however, two types of Ce{sup 3+} centers were found in all samples due to the occupancy of both Ba{sup 2+} and Ca{sup 2+} sites. So the influence of doping concentration on the preferential site occupancy was studied, and it was found that Ce{sup 3+} ions always preferentially enter Ba{sup 2+} sites at low doping concentration for both samples Ba{sub 2(1-x)}Ce{sub x}Na{sub x}Ca(BO{sub 3}){sub 2} and Ba{sub 2}Ca{sub 1-2x}Ce{sub x}Na{sub x}(BO{sub 3}){sub 2}. In addition, the 5d energy levels and decay behaviors for Ce{sup 3+} in Ba{sup 2+} and Ca{sup 2+} sites, the concentration quenching, and the x-ray excited photon output were evaluated to clearly reveal the luminescence more » features. « less