Gd3+ doping induced microstructural evolution and enhanced visible luminescence of Pr3+ activated calcium fluoride transparent ceramics

Transparent Pr3+ doped Ca1-xGdxF2+x (x = 0, 0.01, 0.03, 0.06, 0.10, 0.15) polycrystalline ceramics with fine-grained microstructures were prepared by the hot-pressing method. The dependence of microstructure, optical transmittance, luminescence performances and mechanical properties on the Gd3+ concentrations for Pr3+:Ca1-xGdxF2+x transparent ceramics were investigated. The Gd3+ ions show positive effects on the microhardness of Pr3+:Ca1-xGdxF2+x transparent ceramics as a result of the decrease in the grain sizes. Excited by the Xenon lamp of 444 nm, typical visible emissions located at 484 nm, 598 nm and 642 nm were observed. Furthermore, the incorporation of Gd3+ ions can greatly enhance the photoluminescence performance owing to the improvement in the concentration quenching effect. The quenching concentration of Pr3+ ions in CaF2 transparent ceramics increased to 1 at.% as a result of the positive effect of Gd3+ codoping. The energy transfer mechanism of Pr3+ in the Pr3+:Ca1-xGdxF2+x transparent ceramics has been investigated and discussed.