X-ray and photoluminescence study of Li₆Gd(BO₃)₃:Tb³⁺, Dy³⁺ Phosphors

This work is particularly dedicated to the synthesis of Li₆Gd(BO₃)₃: Tb³⁺, Dy³⁺ (lithium gadolinium borate) phosphors by the well-known solid state reaction method and their X-ray and photoluminescence investigations. The optimal activator's concentrations (0.2 mol% for Tb³⁺ and 0.3 mol% for Dy³⁺) were determined and used for further analysis. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used for analyzing the phases, crystallinities, grain sizes and the overall morphologies of the synthesized phosphors. The X-ray and UV-VIS induced luminescence were measured. The UV induced emission spectrum of Li₆Gd(BO₃)₃: Tb³⁺ phosphor showed five major peaks corresponding to the characteristic Tb³⁺ transitions (⁵D_j →⁷F_j), whereas, Li₆Gd(BO₃)₃: Dy³⁺ phosphor exhibited four major emission peaks that correspond to transitions from the ground state of f⁹(⁶H_15/2) to some higher energy states of 4f⁹. The quantitative analyses of luminescence of the synthesized phosphors are vital for their applications in various fields. Hence, the X-ray induced light yields were measured for Li₆Gd(BO₃)₃: Tb³⁺, Dy³⁺ phosphors to be 113% and 78% of that of gadox (gadolinium oxy sulfide, Gd₂O₂S: Tb³⁺), respectively. Hence these phosphors could be good candidates for X-ray imaging. According to Blasse's and Dexter's calculations, the dipole-dipole interaction is responsible for concentration quenching mechanism on concentrations of both phosphors. The chromaticity coordinates were measured for Li₆Gd(BO₃)₃: Tb³⁺, Dy³⁺.