First-principles study of the Li(Y/Lu)SiO4:Ce3+,Sm3+ storage phosphor

Abstract

First-principles calculations are carried out to study the native point defects and dopants (Ce3+, Sm3+) in Li(Y/Lu)SiO4 for revealing the mechanism of the optical excitation energy storage properties. The calculated excitation and emission energies, the Stokes shifts as well as the positions of 4f and 5d levels of Ce3+ relative to host band edges show great consistent with the experimental results. The calculated formation energies reveal that the Li vacancies (VLi) and the antisite defects LiY and YLi (or LiLu and LuLi) are always much more energetically favorable than Y or Lu vacancies (VY or VLu) and O vacancies (VO) in Li(Y/Lu)SiO4 under reductive atmospheres. Moreover, according to the calculated charge transition levels of the native point defects and the dopants, the antisite defects YLi (or LuLi) and the dopants Sm3+ (SmY or SmLu) are deemed as electron traps that provide suitable charge transition levels for information storage in Li(Y/Lu)SiO4. Based on our calculations, a mechanism diagram of charge carrier storage and recombination during irradiation and thermal or optical readout is constructed for the storage phosphors Li(Y/Lu)SiO4:Ce3+,Sm3+.