“…The decay curves (Figure ) of Tb 3+ as a function of Dy 3+ concentration in phosphors CLPSF:0.20Tb 3+ , y Dy 3+ ( y = 0, 0.01, 0.05, 0.10, 0.15, and 0.30) were recorded and the corresponding lifetime values were estimated. In some case, the overlap integral of the fluorescence spectrum of the donor and the absorption spectrum of the acceptor during estimation due to weak electron phonon coupling are always omitted with doping of the Dy 3+ ions, the decay profile exhibit nonexponential due to the energy transfer process that takes place between the donor and acceptor ions (nearby Tb 3+ ions), therefore all of the decay curves could be expressed as a nonexponential fitting expression:where I ( t ) is the integral intensity at time t . Herein, the average lifetime values ( τ ) were estimated to be 2.461, 2.319, 2.105, 1.883, and 1.522 ms in the as‐prepared phosphors CLPSF:0.20Tb 3+ , y Dy 3+ with y = 0, 0.01, 0.05, 0.10, and 0.30, respectively.…”