Electronic structure and associated properties of europium-activated strontium tetraborate phosphor

Radiation defects in SrB4O7:Eu2+ crystals

“…[17], the ground state of Eu 2+ is about 3.9 eV higher than the valence band top. Taking into account the estimated band gap width for SBO (about 9 eV [17]), it is obvious that the Eu 2+ ions act as an effective hole traps in SBO crystal. Only traces of Eu 3+ luminescence were detected after irradiation of SBO:Eu 2+ single crystal and powders, probably, due to low oscillator strength of 4f-4f transitions of Eu 3+ ions.…”

“…The arising excess charge may be compensated either due to formation of a radiation-induced strontium vacancy by the impact mechanism or due to local deformation of the boron-oxygen framework, since Eu 3+ ionic radius is smaller than that of Eu 2+ ion (1.09 and 1.31Å for coordination number 6, respectively). The fact that SBO:Eu 2+ crystals show a TSL even after a UV irradiation [17] allows one to suppose that the charge compensation occurs according to the second mechanism, since the UV energy is clearly insufficient to displace the strontium ion into an interstice. The experimental fact of the europium ions charge state change is confirmed by simulation of the strontium tetraborate electron structure using the molecular orbital method.…”

“…According to Ref. [17], the ground state of Eu 2+ is about 3.9 eV higher than the valence band top. Taking into account the estimated band gap width for SBO (about 9 eV [17]), it is obvious that the Eu 2+ ions act as an effective hole traps in SBO crystal.…”

“…According to Ref. [17], the F center formation in the O(4) oxygen atom position results in three energy levels appearing in the SBO band gap, namely, those lying 0.1 eV above the valence band top, 0.1 eV under the conductivity band bottom and 3.1 eV above the valence band top. The captured electrons are supposed to occupy the first mentioned level [17].…”

Electronic structure and linear optical property of BaSi2N2O2 crystal

“…First-principle methods have been proved to be a powerful theoretical tool for acquiring accurate electronic levels and optical properties of metal compounds [7,8]. The present work attempts to theoretically characterize the band structure and the optical spectrum.…”