Quantitatively Deciphering the Local Structure and Luminescence Spectroscopy of Pr³⁺-Doped Yttrium Lithium Fluoride

Praseodymium (Pr³⁺)-doped LiYF₄ nanophosphors have garnered significant interest for their potential applications in lasers, phosphors, and quantum memories. However, there remains a lack of comprehensive research on the local coordination environment and luminescence spectroscopy of Pr³⁺:LiYF₄ nanocrystals. This study presents the first investigation of the ground-state structure of Pr³⁺:LiYF₄ crystals by employing the crystal structure prediction method, and a [PrF₈]^5- ligand complex with S₄ local symmetry is determined. The complete energy levels of the Pr³⁺ ions in LiYF₄ nanocrystals are unveiled by using our newly developed well-established parametrization matrix diagonalization method. A novel set of free-ion and crystal-field parameters is derived through a good simulation with 45 experimental energy levels. Many of the emissions of Pr³⁺-doped LiYF₄ are successfully reproduced based on Judd-Ofelt theory, and these transitions are comparable to the experimental ones. Moreover, two new prominent emission bands with their peaks at 675 and 849 nm originating from ¹I₆ → ³F₄ and ¹I₆ → ¹G₄ transitions, respectively, are predicted by us for the first time. This study could provide a feasible method to search for practical laser transition channels of solid-state lasers based on Pr³⁺: LiYF₄ nanophosphors.