Ionic liquid-assisted two-phase synthesis of Lu7O6F9:Yb3+, Er3+ phosphors and their morphological control, color-tunable up-conversion luminescence and temperature sensing behavior

Abstract In this work, Lu7O6F9 microcrystals with various novel morphologies, including hand broom-like nanorods, nanoparticles, hexagons, spindle-like nanoparticle aggregates, hexagonal prisms and microrods, were prepared via ionic liquid-assisted two-phase method and following calcination approach. Ionic liquid was used as F- resource, morphology controller and two-phase solvent. The effect of preparation condition on the phases and morphologies of the precursors as well as the calcined products was studied in detail. The crystallographic structure of Lu7O6F9 was also confirmed by the down-conversion (DC) spectra of Lu7O6F9: Eu3+ phosphor with Eu3+ ion as the structure probe. Besides, different concentration of Yb3+ ions were introduced to the host to obtain Lu7O6F9: Yb3+, Er3+ phosphors, in case of subsequent investigation on the up-conversion (UC) luminescence properties, UC mechanism and followed temperature sensing behavior. Color-tunable UC emissions were realized and the mechanism was discussed. Furthermore, the optical temperature sensing behavior of orthorhombic Vernier lutecium oxyfluoride was investigated for the first time. The influence of Yb3+ content on the sensing sensitivity was also elaborated. These results imply that the as-prepared Lu7O6F9: Yb3+, Er3+ phosphors could be considered as candidates in color-tunable displaying and optical thermometers.