Controlling disorder in the ZnGa${}_2$O${}_4$:Cr${}^{3+}$ persistent phosphor by Mg${}^{2+}$ substitution

Abstract

We have studied in this work the effect of increasing structural disorder on the persistent luminescence of Cr${}^{3+}$ doped zinc gallate spinel. This disorder was introduced by progressive substitution of Zn${}^{2+}$ by Mg${}^{2+}$ 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 Mg/Zn substitution decreases the number of Cr${}^{3+}$ in undistorted sites, and increases the number of Cr${}^{3+}$ with neighbouring antisite defects and with neighbouring Cr${}^{3+}$ ions (referred 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${}^{3+}$ spectra with three types of Cr${}^{3+}$ 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${}^{3+}$ ions.

References in corpus (2)

• The importance of inversion disorder in the visible light induced persistent luminescence in Cr${}^{3+}$ doped AB${}_2$O${}_4$ (A = Zn or Mg and B = Ga or Al)
• Order and disorder around Cr${}^{3+}$ in chromium doped persistent luminescence AB${}_2$O${}_4$ spinels