Lanthanide doped Y₆O₅F₈/YF₃ microcrystals: Phase-tunable synthesis and bright white upconversion photoluminescence properties

High-quality Y₆O₅F₈/YF₃ microcrystals have been synthesised by using a hydrothermal and subsequent calcination route. Upon changing the initial solution pH value, the as-prepared microcrystal can be well tuned from YF₃ octahedron microcrystals to YF₃ hollow spheres and finally to Y₆O₅F ₈ microtubes. The as-obtained microcrystals have been characterised by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and photoluminescence (PL) spectra. When the Y₆O ₅F₈:Ln³⁺ microtubes are excited by a 980 nm continual wave laser diode, bright red, green, and blue room temperature upconversion PL emissions have been observed. A series of white light emissions have been obtained by precisely adjusting dopants concentration in Y ₆O₅F₈ microtubes.