Investigation on structure and photoluminescence properties of Ho 3+ doped Ca 3 (VO 4 ) 2 phosphors for luminescent devices.

This study focuses on the synthesis and characterization of Ho 3+ doped Ca 3 (VO 4 ) 2 phosphor for potential application in solid-state lighting technology. A citrate-based sol-gel process is optimized to achieve sheet-like morphologies in the phosphor material. The investigation reveals UV absorption at 371 nm, indicating a band gap of 3.28 eV. Emission transitions at (506, 541, and 651) nm are observed when excited at 451 nm, with an optimal Ho 3+ concentration of 0.05 mol resulting in robust green emission at 541 nm. The concentration quenching in Ca 3 (VO 4 ) 2 : x Ho 3+ phosphors is discussed in detail with Blesse's and Dexter's models. The concentration quenching effect found in the studied samples is due to the dipole-dipole interactions. Judd-Ofelt intensity parameters were calculated from the excitation bands, and for Ω 2 , Ω 4 , and Ω 6 are (0.16, 0.17, and 0.36) × 10 -20 cm 2 , respectively. The emission properties for the ( 5 S 2 + 5 F 4 ) → 5 I 8 and 5 F 5 → 5 I 8 transitions are also estimated with J - O parameters. The higher magnitude of branching ratios (83%) and emission cross-sections (1.6 × 10 -21 cm 2 ) suggest that the Ca 3 (VO 4 ) 2 :0.05Ho 3+ phosphor materials may be suitable for efficient green-emitting device applications. The CIE coordinates confirm the potential of Ho 3+ -doped phosphors for green emissions, making them suitable for solid-state lighting and display technology.