Luminescence of manganese and chromium ions in spinel hosts

Single-phase ceramic samples of MgAl$_2$O$_4$, ZnAl$_2$O$_4$ and LiAl$_5$O$_8$ spinels containing manganese or chromium ions have been synthesized by a high-temperature solid-state reactions method. It has been shown that the luminescence properties of the synthesized phosphors, in particular, the appearance of intense red luminescence from Mn$^{4+}$ ions, as well as the magnitude of inhomogeneous line broadening in the luminescence spectra of Mn$^{4+}$ and Cr$^{3+}$ ions depend on the degree of cation inversion, which provides the charge compensation for stabilizing Mn$^{4+}$ ions in the octahedral sites of the spinel structures upon the substitution of Al$^{3+}$ ions, simultaneously resulting in disordered spinel crystal structures.