Color-tunable Luminescence via Valence-state modulation in Mn-doped Zn2Sn1-xTixO4

초록

Transition-metal-doped phosphors have emerged as sustainable alternatives to rare-earth ion-based phosphors. These materials address concerns related to resource criticality and cost while providing versatile optical tunability. The flexible cation distribution in inverse-spinel oxides enables selective stabilization of oxidation states of transition metal ions. Herein, we report Mn-doped Zn2Sn1-xTixO4 (0 <= x <= 1) as a model system for demonstrating valence-state engineering through B-site substitution. Structural analyses confirmed a continuous inverse-spinel solid solution accompanied by monotonic lattice contraction. Rietveld refinement further revealed systematic decreases in the cation-oxygen bond lengths. Interestingly, the Mn-O bond length in tetrahedral and octahedral complexes exhibit opposing trends, exhibiting progressive destabilization of Mn2+ in the tetrahedral sites but enhanced stabilization of Mn4+ in octahedral coordination as x increased. The photoluminescence spectra revealed a distinct color evolution from green (Mn2+) to red emission (Mn4+), demonstrating effective compositional control over the emission color. These results validate valence-state engineering for developing next-generation, color-tunable phosphors.

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