Modulation strategy of manganese valence state in yttrium gallium garnet

Abstract

Different manganese ions (Mn2+, Mn3+, and Mn4+) can be stabilized in garnet hosts, while the relevant stabilization problem of Mn2+ ions remains elusive. In this study, combined with co-doping Si4+ ions and reduction processing, Mn2+ ions are successfully stabilized in the Y3Ga5O12 (YGG) gallium garnet host, and the relevant stabilization mechanism is analyzed in detail. The obtained result indicates that the introduction of Si4+ can speed up the conversion from Mn4+ and Mn3+ ions to Mn2+ ones effectively, and the introduced Mn2+ ions can occupy two kinds of doping sites in the YGG lattice, corresponding to eight-coordinated Y3+ sites and six-coordinated Ga3+ sites. The dodecahedral Mn2+ ions manifest a stronger fluorescence intensity than that of the octahedral Mn2+ ions, and the increase of Si4+-doped content is more beneficial to enhance the photoluminescence performance of the octahedral Mn2+ ones. Additionally, octahedral Mn2+ ions exhibit a larger Huang-Rhys factor (S) value (S = 3.41) than that of dodecahedral Mn2+ ions (S = 1.34), meaning that the six-coordinated Mn2+ sites demonstrate a much stronger electric-phonon coupling strength. Finally, the temperature sensing strategy based on the temperature-dependent fluorescence distinctions between the two kinds of Mn2+ sites in the YGG host is also proposed, further proving the application potential of Mn2+ ions in the field of optical thermometry.