Suppressed Self‐Reduction of Manganese in Mg2SnO4 via Li+ Incorporation with Polychromatic Luminescence for Versatile Applications

Herein, the self‐reduction behavior of manganese (Mn) in Mg2SnO4 (MSO) host lattices prepared by using the solid‐state reaction technique in air atmosphere is reported. Excited by 282 nm, only the emission of Mn2+ is seen, and the observed results are confirmed by theoretical calculation based on the density functional theory. Noteworthy, with the codoping of Li+, the self‐reduction process of Mn is suppressed, leading to the coexistence of Mn2+ and Mn4+ in MSO host lattices along with the multicolor emissions. For the suppressed self‐reduction behavior, possible hypotheses are proposed to elucidate the corresponding mechanisms. Furthermore, benefiting from the different thermal quenching behaviors of Mn2+ and Mn4+, ratiometric optical thermometers with high sensitivity of 6.59% K−1 are designed. Moreover, the prepared phosphors possess a good green afterglow phenomenon, in which their trap depth are 0.71 and 0.91 eV. In addition, via using the designed phosphors, applications in anti‐counterfeiting, fingerprint identification, and optical information storage are also realized. The self‐reduction behavior of Mn4+/Mn7+ to Mn2+ is achieved in Mg2SnO4 phosphors prepared in air atmosphere. Moreover, the self‐reduction behavior of Mn can be suppressed by the addition of Li+, resulting in the coexistence of Mn2+ and Mn4+, and even the Mn2+ and Mn4+ concentrations can be accurately regulated by changing the Li+ content.