Controlling disorder in the ZnGa₂O₄:Cr³⁺ persistent phosphor by Mg²⁺ substitution

Abstract

We have studied in this work the effect of increasing structural disorder on the persistent luminescence of a Cr doped zinc gallate spinel. This disorder was introduced by progressive substitution of Zn by Mg ions, and was studied by photoluminescence, X-ray diffraction, extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES) and electron paramagnetic resonance (EPR) spectroscopy. It was found that increasing the Mg/Zn substitution decreases the number of Cr in undistorted sites and increases the number of Cr with neighbouring antisite defects and with neighbouring Cr ions (referred to as Cr clusters), which in turn decreases the intensity of persistent luminescence. Both XANES and EPR spectra could be simulated by a linear combination of Cr spectra with three types of Cr environments. The increasing disorder was found to be correlated with a decrease of the average Cr-O bond length and a decrease of crystal field strength experienced by Cr ions.

Predicting the afterglow duration in persistent phosphors: a validated approach to derive trap depth distributions

“…[26][27][28][29] Alternatively, exploring variations in host composition can lead to the appropriate trap depth variation as well. [30][31][32][33][34] Usually, and especially with e.g. transition metals or main group ns 2 ions, these modifications are still done via a rather inefficient trial-and-error approach, as the studies for these elements provide empirical rules with more limited applicability, due to substantial uncertainties caused by their much stronger crystal field interactions and larger number of possible valence states, although recently considerable progress was made.…”

Counting the Photons: Determining the Absolute Storage Capacity of Persistent Phosphors

“…An important class of these materials are the red- and infrared-emitting persistent phosphors, which are quite scarce compared to other classes, but are highly desired in diverse applications, such as bioimaging and safety signage. These phosphors are expected to exhibit efficient afterglow and are often based on the luminescence of transition metal ions [10,11,12]. …”

Probing the local structure of the near-infrared emitting persistent phosphor LiGa5O8:Cr3+

“…[14][15][16][17] A model for the mechanism of persistent luminescence in ZGO:Cr has been developed throughout the years by a combined analysis of data obtained via different techniques. [18][19][20][21] The currently accepted model attributes the afterglow behavior to the interaction between the Cr 3+ ion and nearby anti-site defects in ZGO spinel.…”