Critical effects of annealing under carbon atmosphere on the structural and persistent luminescent properties of Zn2TiO4:Cr3+

Abstract

Persistent luminescence (PersL) emitting materials have garnered significant interest due to their applications in bioimaging, radiation detection, and anticounterfeiting. This study investigates the impact of annealing in a reductive carbon atmosphere on the structural, optical and PersL properties of Cr³⁺-doped Zn₂TiO₄ inverse spinel. X-ray diffraction (XRD) coupled with UV–visible absorption spectra confirmed the preservation of the Zn₂TiO₄ phase. PersL studies after UV (254 nm and 365 nm) and X-rays pre-excitation demonstrated that air-annealed samples exhibit prolonged afterglow due to effective charge trapping, whereas, carbon annealed samples undergo significant PersL quenching, indicating altered defect states and recombination pathways. X-rays excited optical luminescence (XREOL) measurements reveal distinct emission behaviors, with carbon annealing inducing quenching of PersL, suggesting modified trap depth and charge carrier interactions. Strong thermal quenching in air-annealed samples and anti-thermal quenching of the steady state photoluminescence in carbon-atmosphere annealed samples upon excitation at 340 nm is obtained. We anticipate that the Zn and oxygen vacancies dominate the overall luminescence mechanism. This study provides new insights into defect engineering in PersL phosphors, paving the way for optimized luminescent materials for bioimaging, radiation detection, and next-generation phosphor applications.