Pulse Cathodoluminescence of the Impurity Centers in Ceramics Based on the MgAl₂O₄ Spinel

The spectral and luminescence decay kinetics of magnesium aluminate spinel ceramics prepared by spark plasma sintering (SPS) and the starting nanopowders were studied. It was demonstrated that two types of luminescence in spinel ceramics can be observed after pulse e-beam excitation. The first type is due to intrinsic defects, and the second type due to Cr³⁺ and Mn²⁺ ions. It was shown that the luminescence decay kinetics for Cr³⁺ and Mn²⁺ impurity ions can be approximated by the sum of two exponents. The decay times for the Cr³⁺ ion are 35 and 409 ns, for the Mn²⁺ ion are 29 and 340 ns. High-temperature exposure during SPS synthesis does not lead to a change in the nearest surroundings of impurity ions. In the luminescence spectra of ceramic and powder samples the intensity ratio changes of intrinsic and impurity centers is associated with strong diffuse scattering of light for spinel nanopowders.