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

Abstract

A series of Ca₁₀(PO₄)₆F₂:Er³⁺ phosphors doped with varying concentrations of Er³⁺ 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 Er³⁺ 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 ²H_11/2 → ⁴I_15/2 and ⁴S_3/2 → ⁴I_15/2 transitions of Er³⁺ 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.