Energy transfer mechanism and luminescence properties of green phosphors Sr2YF7: Dy3+, Tb3+

In this study, color-adjustable Sr2YF7: xDy3+, and yTb3+ light-emitting phosphors were synthesized through the hydrothermal method. Systematic experiments were performed to determine the optimal doping concentration for Sr2YF7: xDy3+ phosphor with x = 0.03, resulting in a distinctive light blue emission band attributed to the 4F9/2 → 6H15/2 transition. The energy transfer within the double-doped system of Sr2YF7: Dy3+, yTb3+ (y = 0, 0.06–0.1) was examined by analyzing spectral overlap and reductions in emission lifetimes. Moreover, the mechanism governing this energy transfer phenomenon was investigated. The concentration proportion of Dy3+/Tb3+ in Sr2YF7 phosphors was modulated to achieve color modulation, transitioning from light blue to vibrant green emissions in Sr2YF7: Dy3+, Tb3+ samples. The intensity of green emission increased with increasing Tb3+ ion concentrations because of the dynamics of energy migration from Dy3+ to Tb3+ levels (4F9/2 + 7F6 → 6H15/2 + 5D4). Based on calculations using steady-state rate equations, Tb3+ ion doping effectively reduced ionic spacing and consequently amplified the green emission. Furthermore, the results indicated that the luminous intensity ratio of Sr2YF7: 0.03Dy3+, 0.07 Tb3+ phosphors at 423/303K was notably high at 93.59 %, indicating high thermal stability. Thus, Sr2YF7 phosphors co-doped with Dy3+ and Tb3+ emerge as potential candidates for application in advanced illumination technologies.