Specific Features of Formation of Electron and Hole Trapping Centers in Irradiated CaSO4-Mn and BaSO4-Mn

Abstract

Spectroscopic and thermoactivation methods were used to study the processes of accumulation of electron and hole trapping centers and energy transfer of electronic excitations to impurities in CaSO4-Mn and BaSO4-Mn. It is shown that electronic trapping centers are created during the excitation of an anionic complex as a result of charge transfer from O2−→SO42− to closely spaced anionic complexes SO42− in CaSO4 and BaSO4. In CaSO4 and BaSO4, energy transfer from the host to impurities occurs at the moment of charge transfer from the excited anionic complex to the combined radiative electronic state at 2.95–3.1 eV. This combined state is formed from electronic trapping centers Mn+-SO4− and SO43−-SO4−. It was found that the emerging combined radiative states at 2.95–3.1 eV of sulfates, which are formed as a result of charge transfer from the excited anionic complexes to the excited state of impurities, Tl+,Cu+,and Mn2+, occupy the same energy levels as the intrinsic electronic trapping center SO43− of the host at 2.95–3.17 eV. Experimental results show that during UV photon irradiation, anionic complexes are excited mainly near impurities in sulfates.

Luminescence and Electron–Hole-Trapping Centers in α-Ca2P2O7−Mn

“…In the studies by authors [20,21], the mechanisms for the accumulation of intrinsic and impurity electron-hole-trapping centers were explored in both pure and Mn 2+ -activated CaSO 4 and BaSO 4 . It was demonstrated that intrinsic SO 3− 4 − SO − 4 and impurity Mn + − SO − 4 trapping centers form as a result of free electrons localizing on the SO 2− 4 anion and Mn 2+ impurities, through the reactions SO 2− 4 + e − → SO 3− 4 and Mn 2+ + e − → Mn + .…”