Photoluminescence and Crystal-Field Analysis of Reddish CaYAl3O7: Eu3+ Phosphors for White LEDs

Red melilite structure CaY_1-<i>x</i>Al₃O₇: Eu<i>_x</i> (<i>x</i> = 0.04-0.24) phosphors for white LEDs were synthesized through a straightforward solid-state reaction process. These phosphors exhibit efficient excitation under near-ultraviolet light at 398 nm (⁷<i>F</i>₀ → ⁵<i>L</i>₆), producing the desired emission peak at 622 nm from the transitions of ⁵<i>D</i>₀ → ⁷<i>F</i>₂. The Eu doping concentration was also optimized as <i>x</i> = 0.16. The complete 3003 × 3003 energy matrix was constructed based on an effective Hamiltonian including both free-ion and crystal-field interactions within a complete diagonalization method (CDM). Eighteen experimental fluorescent spectra for Eu³⁺ ions at the Y³⁺ site of CaYAl₃O₇ crystal were quantitatively identified with high accuracy through fitting calculations. The fitting values are in reasonable agreement with the experimental results, thereby showcasing the efficacy of the CDM in probing luminescent phosphors for white LEDs.