Enhanced luminescence of a new red phosphor Na13Sr2Ta2(PO4)9:Eu3+ by co-doping charge compensators Li+/Na+/K+

Abstract

A new type of red emitting phosphor Eu3+-doped Na13Sr2Ta2(PO4)9 (NSTP) was synthesized by high temperature solid-state method. The effects of Eu3+ doping concentration on crystal structure and optical properties were studied by powder X-ray diffraction (XRD), steady state and transient state fluorescence spectroscopy. NSTP:Eu3+ phosphors glowed red light when stimulated by near-ultraviolet light of 394 nm, due to the 4f→4f transitions of Eu3+. The optimal Eu3+ doping concentration in NSTP host matrix was determined to be x = 0.2, excess dopant will lead to concentration quenching due to the dipole-dipole interaction. At 420 K, the relative luminous intensity remains about 76% of the initial intensity at 300 K, which shows that NSTP:0.2Eu3+ phosphor has good thermal stability. Furthermore, three alkali metal ions, Li+, Na+ and K+ were introduced as charge compensators to improve luminescent efficiency. In comparison, all three compensators can enhance the luminescence intensity, in which the self-compensating ion Na+ is the best one. The internal quantum yield (IQY) of phosphor NSTP:0.2Eu3+,0.2Na+ was measured to be 44.94%, suggesting its potential application in LEDs as a red component.