Improved ultraviolet -visible optically transmittance and luminescent properties in Yb, Lu: Sr5(PO4)3F transparent ceramics via Lu3+ co-doping

The asymmetric hexagonal Sr5(PO4)3F (S-FAP) crystal material is considered to be the most suitable solid state laser gain medium for small laser diode pumping in the future due to its large absorption, emission interface, and long fluorescence lifetime. However, the mediocre optical transmittance of S-FAP transparent ceramics and the degradation of luminescence properties due to the doping of Yb activated ions seriously hinder its application prospects. In view of this, a series of 0.02Yb, xLu: S-FAP (x = 0–0.02) transparent ceramics with excellent optical properties were synthesized by hot pressing sintering. The powder SEM results show that Lu doping has no obvious effect on the morphology, grain size, and dispersion of powder. The linear transmissivity curves show that the ultraviolet (200 nm) and visible (500 nm) transmissivity increase by 54 % and 17 %, respectively, with Lu doping compared with the undoped ceramic samples. The surface SEM of ceramics revealed that Lu3+ promoted the increase of ceramic grain size significantly. The emission spectrum and fluorescence decay curves at room temperature also show that the emission intensity and fluorescence lifetime of ceramic samples increase significantly with Lu co-doping.