Investigation on structure and photoluminescence properties of Ho3+ doped Ca3(VO4)2 phosphors for luminescent devices.

Abstract

This study focuses on the synthesis and characterization of Ho3+ doped Ca3(VO4)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 Ho3+ concentration of 0.05 mol resulting in robust green emission at 541 nm. The concentration quenching in Ca3(VO4)2:xHo3+ 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 cm2, respectively. The emission properties for the (5S2 + 5F4) → 5I8 and 5F5 → 5I8 transitions are also estimated with J-O parameters. The higher magnitude of branching ratios (83%) and emission cross-sections (1.6 × 10-21 cm2) suggest that the Ca3(VO4)2:0.05Ho3+ phosphor materials may be suitable for efficient green-emitting device applications. The CIE coordinates confirm the potential of Ho3+-doped phosphors for green emissions, making them suitable for solid-state lighting and display technology.