Structural and optical properties of Mg _{1− x} Mn _x P ₂ O ₆ ( x = 0–1.0) magnesium metaphosphate

Abstract Structural and optical properties of Mg 1− x Mn x P 2 O 6 ( x = 0–1.0) magnesium metaphosphate were investigated in detail. The complete solid solution of MgP 2 O 6 –MnP 2 O 6 is confirmed as monoclinic space group C 2/ c . The dynamic luminescence was studied by changing the Mn 2+ content (0–100 mol%) and temperature (10–300 K). There is a good chemical homogeneity in Mg 1− x Mn x P 2 O 6 ( x = 0–1.0), which can be supported by the linearly varying cell size and the gradually changing vibration spectrum. However, the optical properties of the solid solution do not show a continuous change trend, that is, an obvious inflection point appeared when x = 0.5. Mg 1− x Mn x P 2 O 6 ( x = 0.1–0.5) shows a dominant O 2− → Mn 2+ charge transfer (CT) absorption in the near UV region and feeble d–d transitions of Mn 2+ in visible wavelength region. However, Mg 1− x Mn x P 2 O 6 ( x = 0.6–1.0) presents a strong d–d absorption transition and nearly disappeared CT band. The changing trend of optical absorption is also maintained in the excitation and emission of the solid solutions. In Mg 1− x Mn x P 2 O 6 ( x = 0.1–0.5), (Mn, Mg)O 6 octahedron has slight distortion, and the effective luminescence only occurs when CT band excitation is used. In contrast, in Mg 1− x Mn x P 2 O 6 ( x = 0.6–1.0), (Mn, Mg)O 6 octahedron is highly distorted, and only excitation at d–d transition produces effective luminescence. This research highlights the critical role of MnO 6 octahedral distortions in the luminescence properties of Mn 2+ activators. The research provides a reference for developing optical materials.