The enhancing luminescence of B2O3-doped SrAl2O4: Eu2+, Dy3+ single crystals

Abstract

A series of 1.5–3.5 mol% B₂O₃-doped SrAl₂O₄: Eu²⁺, Dy³⁺ single crystals were successfully grown by the optical floating zone method for the first time. XRD and Raman spectroscopy revealed that the samples were monoclinic, with good crystallinity and no phase transition. The cell refinement results indicate that the cell volume decreases with B³⁺ ions. The intensities of both the excitation and emission characteristics of the crystal samples were enhanced after the incorporation of B³⁺, surpassing those observed in pure SrAl₂O₄: Eu²⁺, Dy³⁺ crystals. This enhancement is attributed to the facilitated entry of Eu²⁺ into the lattice upon B³⁺ addition, resulting in an increased number of 4f⁶5 d¹-4f⁷ charge transfer transitions. Long afterglow lifetime spectra disclosed that samples with 3 mol% B₂O₃ concentration achieved the longest afterglow duration, extending up to 139 s, whereas samples lacking B₂O₃ lasted 34 s. Thermoluminescence analysis showed that defect concentration escalated with B³⁺ concentration increments, reaching a maximum at the 3 mol% B₂O₃, beyond which it declined. Finally, the long afterglow luminescence mechanism proposed by Dorenbos is further explained and confirmed. It is concluded that B³⁺ doping increases the defect concentration by altering the crystal's microstructure, which in turn enhances both the luminescence performance and the long afterglow performance of the SrAl₂O₄: Eu²⁺, Dy³⁺ single crystal.