Exploring site-selective photoluminescence of Eu3+ and Tb3+ ions in Sr10(PO4)6F2 and the development of different phosphor materials

Abstract

We have developed a wide range of phosphor materials with varying color characteristics in the green, yellow, orange, and red regions based on Sr10(PO4)6F2 matrix and different compositions of Eu3+ & Tb3+ ions. The site-selective Tb3+→Eu3+ energy-transfer dynamics found to play a great role for such tunable color characteristics. DFT based calculations were performed to understand the preference of lattice-site occupancy of the two dopant ions, which suggested that while Eu3+ ion prefers both Sr1 & Sr2 sites; Tb3+ only prefers Sr1 site. The site selective distribution has immediate impact on the photoluminescence lifetime values, wherein two different components were observed for both the dopant ions. In case of Eu3+ ion, the short-lived lifetime component of Eu3+ ion is originated when it is placed at Sr1 site and the long-lived component at Sr2 site, which has F-atom in its coordination and provides extra stability to the excited state at Sr2 site. However, for Tb3+ ion, the two lifetime components are explained based on the energy-transfer probability. The site-selective luminescence of Eu3+ & Tb3+ ions was found to play the key role while developing colour tuneable phosphor materials.