Luminescence properties and mechanisms of Ca10(PO4)6F2:Er3+ as a green phosphor for white LEDs

A series of Ca 10 (PO 4 ) 6 F 2 :Er 3+ phosphors doped with varying concentrations of Er 3+ concentrations (2–14 mol.%) have been synthesized via a hydrothermal method to investigate their optical spectroscopy and temperature-sensing properties. Rietveld refinements of the XRD data reveal that Er 3+ ions preferentially occupy Ca2 sites rather than Ca1 sites to reduce electrostatic repulsion between cations within the fluorapatite lattice. Morphological characterization using SEM, TEM, and EDS confirms that the synthesized phosphors exhibit a rod-like morphology with dimensions of approximately 2.5 μm in length and 1 μm in diameter, along with an excellent single-crystal structure and uniform elemental distribution. Under 378 nm excitation, the phosphors exhibit prominent green emission peaks corresponding to the 2 H 11/2  →  4 I 15/2 and 4 S 3/2  →  4 I 15/2 transitions of Er 3+ ions. The optimal dopant concentration is determined to be 10 mol.%, with a calculated critical distance of 9.98 Å, indicating that electric quadrupole–quadrupole interactions dominate the concentration quenching mechanism. The luminescence lifetime of the optimized phosphor has been measured as 0.604 ms. Additionally, the chromaticity coordinates (0.3127, 0.6723) and high color purity (98.06 %) highlight the potential applicability of this phosphor in white light-emitting diodes (LEDs) and other optoelectronic devices.