Multiple morphologies of YF₃: Eu³⁺ microcrystals: Microwave hydrothemal synthesis, growth mechanism and luminescence properties

Uniform and well-crystallized orthorhombic YF₃:Eu³⁺ phosphors with different morphologies (rod-like, spindle-like and gearwheel-like) were prepared by a facile microwave-assisted hydrothermal method. The as-synthesized products were systematically characterized by X-ray powder diffractometer (XRD), thermal field emission scanning electron microscope (FE-SEM), high resolution transmission electron microscope (HRTEM), and photoluminescence (PL) spectrometer. The results indicate that reaction temperature and time have great impact on the morphology and size of the products. A possible formation mechanism of the micro-gearwheel like particle was proposed based on the time-dependent experiments and HRTEM results. The emission spectrum recorded for an excitation wavelength of 392 nm exhibited a strongest emission peak centered at 592 nm, corresponding to the magnetic dipole of the ⁵D₀→⁷F₁ transition of Eu³⁺ ions. The quenching concentration was found at 20 mol% doping of Eu³⁺. The investigation on morphology-dependent luminescence properties reveals that the gearwheel-like YF₃:Eu³⁺ powders exhibit the strongest orange-red emission, while the intensity of rod-like ones is the lowest.