Vcenters inMgAl2O4spinels

Abstract

V centers induced by ionizing irradiation at 80 or 300 K in single-crystal and polycrystalline ${\mathrm{MgAl}}_2$ ${\mathrm{O}}_4$ samples have been studied by use of electron paramagnetic resonance and optical absorption. ${\mathit{V}}_{\mathit{t}}^{\mathrm{-}}$ and ${\mathit{V}}_{\mathit{o}}^{2\mathrm{-}}$ centers, as a result of hole trapping at tetrahedral and octahedral cation vacancies, respectively, have been found to be responsible for two EPR bands centered at g=2.011 and optical absorption bands involved in the complex absorption spectrum at about 3.4 eV. These centers anneal thermally in a very wide step from 220 to 575 K.