Tuning optical properties of Mn5+ doped Ba3(VO4)2: Pigment and phosphor

The Ba₃(V_1-xMn_xO₄)₂ solid solution was synthesized using both a conventional ceramic route and the sol–gel Pechini process. Structural and compositional characterization was performed using X-ray diffraction, Raman spectroscopy, and EPR, enabling a detailed understanding of how Mn content influences both structure and color. These compounds exhibit a dual optical behavior: (i) strong absorption in the visible to near-infrared range due to Mn⁵⁺ intra-atomic transitions, and (ii) intense absorption in the UV–visible range resulting from ligand-to-metal charge transfer (LMCT) involving both Mn⁵⁺ and V⁵⁺. This dual absorption gives rise to a narrow reflection window centered on blue hues, allowing the color to be tuned from pale blue to dark green depending on the manganese concentration. Additionally, compositions with low Mn content display a sharp and intense near-infrared emission at 1181.5 nm, though this emission is strongly quenched at higher Mn levels. These findings highlight the potential of these compounds as stable and non-toxic inorganic pigments with interesting optical properties.