Pr3+-Activated Sr2LaF7 Nanoparticles as a Single-Phase White-Light-Emitting Nanophosphor

Sr₂LaF₇:<i>x</i>Pr³⁺ (<i>x</i> = 0.2, 1, 2, 3, 5, 10, and 25 mol%) nanophosphors with a cubic Fm3m structure were hydrothermally synthesized, forming nearly spherical nanoparticles with an average diameter of approximately 32 nm. Diffuse reflectance measurement and excitation spectra showed a primary excitation peak of Pr³⁺ at 443 nm, corresponding to the ground state to the ³P₂ level transition. Upon blue light excitation, Pr³⁺-activated Sr₂LaF₇ nanophosphors showed rich emission structure across the visible region of the spectrum, with blue (~483 nm), green (~525 nm), orange (~600 nm), and red (~640 nm) emissions, blue and orange being the most prominent ones. The relative intensities of these emissions varied with Pr³⁺ concentration, leading to tunable emission colors. The chromaticity showed slight variation with the Pr³⁺ content (0.350 < x < 0.417, 0.374 < y < 0.380), while the CCT value increased from 3118 K to 4901 K as the doping concentration increased. The optimized Sr₂LaF₇ with 2 mol% Pr³⁺ had the most intense emission with correlated color temperature (CCT) of 3628 K, corresponding to the warm white color. The proposed Pr³⁺-doping strategy offers valuable insights into discovering or optimizing single-phase phosphors for white-light-emitting applications.