Intense upconversion luminescence and origin study in Tm3+/Yb3+ codoped calcium scandate

Doping concentration optimized CaSc2O4:0.004Tm(3+)/0.1Yb(3+) shows stronger upconversion luminescence (UCL) than doping concentration also optimized typical oxide upconverting phosphor Y2O3:0.004Tm(3+)/0.1Yb(3+) upon 980 nm laser diode pump. The two-step up converted H-3(4) -> H-3(6) near infrared emission peaked around 800 nm and the three-step up converted (1)G(4) -> H-3(6) blue emission around 480 nm of Tm3+ is enhanced by a factor of 3.5 and 2.2, respectively. On analyzing the F-2(5/2) -> F-2(7/2) emission intensities and decay curves of Yb3+ in the two hosts, we reveal that Yb3+ in CaSc2O4 exhibits both a larger absorption cross section at 980nm and Yb3+ -> Tm3+ first step energy transfer coefficient (9.29 x 10(-17) cm(3) s(-1)) than that (2.87 x 10(-17) cm(3) s(-1)) in Y2O3, indicating that CaSc2O4 is an excellent host for achieving very intense UCL in Tm3+/Yb3+ codoped oxide upconverting materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4753802]