Electronic structure, morphology-controlled synthesis, and luminescence properties of YF₃: Eu³⁺

Studying electronic structure plays a key role in improving the photoluminescence (PL) properties of materials. Therefore, the electronic structure of YF₃: xEu³⁺ with different Eu³⁺ ions doping concentrations was explored by first-principles calculations based on density functional theory (DFT). As calculated, the YF₃ host had an indirect bandgap of 7.68 eV. From all calculation results we got, the band structure of YF₃: xEu³⁺ exhibited the smallest direct band gap of 6.54 eV when the value of x was 0.10. This small direct band gap is beneficial to obtain excellent emission intensity. Besides, the morphologies and sizes have a significant influence on the fluorescence intensity of the products. A series of YF₃: xEu³⁺ phosphors with leaf-like, spindle-like, pecan-like, and granular-like morphologies were obtained by changing the RE³⁺/NaF ratio via a microwave hydrothermal method. At the same time, the formation process of granule-like YF₃: Eu³⁺ was explored through time-dependent experiments. Furthermore, the fluorescence performance of YF₃: xEu³⁺ was studied in detail. The as-obtained YF₃: xEu³⁺ can exhibit orange-red emission under ultraviolet excitation because of the magnetic dipole of the ⁵D₀–⁷F₁ transition of Eu³⁺ ions. After comparing the luminescence properties of samples with different morphologies, we found that the sample with granule-like morphology had the highest orange-red emission intensity. The experimental result proved that the appropriate Eu³⁺ ions doping concentration were x = 0.10, which is highly consistent with the calculation result. [Figure not available: see fulltext.]