Luminescence of Yb-doped YAG: Divalent ytterbium ions
Abstract This study reports the presence of Yb 2+ ions with 4f 13 6s electron configuration of the ground state in addition to Yb 3+ ions in yttrium aluminium garnet ceramics activated by ytterbium. Pulsed cathodoluminescence and transmission spectra of divalent ytterbium ions appear as narrow lines of s↔s transitions at 913–1050 nm range. These ions in association with oxygen vacancies generate Re–F centres which are able to absorb at 280, 365, 630 nm and emit at 325, 520, 590−720 nm in d↔s transitions of Yb 2+ ions; the emission band at 590–720 nm consists of eight narrow lines. The Re–F centeres are manifested most clearly in the ceramic samples obtained directly after vacuum sintering at 1800 °C.