Theoretical determination of the electronic structures and energy-level splitting for Pr^³⁺-doped Y_₂SiO_₅ crystals

Trivalent praseodymium (Pr^³⁺)-doped yttrium silicate (Y_₂SiO_₅) crystals have been widely used in various phosphors owing to their excellent luminescence characteristics. Although a series of studies have been carried out on its application prospects, the electronic structures and energy-transfer mechanisms of Pr^³⁺-doped Y_₂SiO_₅ (Y_₂SiO_₅:Pr) remain an exploratory topic. Herein, the crystal structure analysis by the particle swarm optimization structure search method is used to study the structural evolution of Y_₂SiO_₅:Pr. Two novel structures with local [PrO₇]⁻¹¹ and [PrO_₆]^⁻⁹ [Y_₂SiO_₅:Pr (I) and Y_₂SiO_₅:Pr (II)] are successfully identified. The impurity Pr^³⁺ ions occupy the Y^³⁺ sites and successfully integrate into the Y_₂SiO_₅ host crystal with a Pr^³⁺ concentration of 6.25%. The calculated electronic band structures show that the doping of Pr^³⁺ induces a reduction in band gaps for the host Y_₂SiO_₅ crystal. The conduction bands near the Fermi level are completely composed of f states. For the atomic energies of Pr^³⁺ in Y_₂SiO_₅, the Stark levels and transitions are properly simulated based on a new set of crystal field parameters (CFPs) at the C_₁ site symmetry. A satisfactory r.m.s. dev. of 15.57 cm^⁻¹ with 9 free ion parameters (plus 27 fixed CFPs as obtained from ab initio calculation) fitted to the 33 observed levels is obtained for the first time. The plentiful energy-level transition lines, from the visible light to the near-infrared region, are deciphered for Pr^³⁺ in Y_₂SiO_₅. Blue ^³P₀ → ^³H_₄ at 465 nm is calculated to be a strong emission line, and it might be an ideal channel for laser actions. These results could not only provide important insights into the rare-earth-doped crystals but also lay the foundation for future research studies of designing the new laser materials. Copyright © 2024 American Chemical Society.