Luminescent properties of a novel near-infrared super-long afterglow material Zn3Al2 Ge2O10:Cr3+

A novel near-infrared afterglow material Zn3Al2 Ge2O10:Cr3+ was synthesized by high-temperature solid-phase method, and analyzed by means of XRD, photoluminescence spectra, curve of afterglow decay, etc. The results indicate that the Zn3Al2 Ge2O10:Cr3+ is in fact ZnAl2O4:Cr3+ spinel compound in which Al3+ is partly replaced by Ge4+. Under 397 nm excitation, the emission spectra at room temperature mainly consist of two obvious narrow peaks superposition on a broadband which belongs to the spin-allowed 4T2→4A2 emission of Cr3+. The concentration quenching and temperature quenching could be observed as the Cr3+ doping concentration and sintering temperature increasing. The optimized LLP performance and the strongest luminescence intensity could be obtained when the doping content of Cr3+(x) in Zn3Al2-x Ge2O10:xCr3+ is 2% and the sintering temperature is 1350°C. The persistence time of the material lasts more than 300 h. The strongest peaks of both emission spectrum and afterglow spectrum are at around 697 nm. The effect of sintering temperature on the LLP performance is analyzed and the mechanism of super long afterglow is researched.