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 Ω2, Ω4, and Ω6 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.