Photoluminescence of Co2+ ions in Mg2SnO4 tetrahedral sites

Wet Chemical Synthesis and Optical Properties of Co2+-Doped Magnesium Stannate Ceramics

“…The observed short radiative lifetimes close to 9 µs is like other Co 2+ -doped systems and associated to spin-allowed electric dipole transitions, which corroborates the transition assignment related to the emission spectra 14,22 . Moreover, the results indicated that the time decay does not change significantly with divalent cobalt doping.…”

“…Phase Proportion (%) 0.34 the divalent cobalt cations tend to occupy Mg 2+ tetrahedral positions, due to their valence similarity 14 . Photoluminescence measurements can help to clarify which site (octahedral or tetrahedral) is preferential for Co 2+ occupation and can also be used to confirm the valence of the emitting cation.…”

“…Similar spectra were also obtained when the same compound containing 0.1 at. mol% of Co 2+ was synthesized via solid state route, exhibiting a broad band peaked at 698 nm under 500 nm excitation 14 . Other authors working with systems using Co 2+ as activator report similar spectra 26,27 .…”

“…This value of the Stokes shift is considered short, and it was found similar for the 0.1 at. mol% of Co 2+ sample (770 cm −1 ) obtained by solid state reaction for this group, leading to a self-absorption process and possible interference from excitation wavelengths in the sample emission 14 . Due to this considerable overlapping, the proximity among Co 2+ ions could lead to a marked luminescence quenching when the Co 2+ level increases above a specific limit which will depend on the kind of occupation site.…”

“…The emission spectra exhibited two bands, the most intense in the 650-780 nm range, accompanied by a weak band in 800-900 nm region. These bands were assigned to Co 2+ transitions in tetrahedral sites 14 .…”