Spectral Investigation of Enhanced Orange Emission in Eu³⁺ Activated LaPO₄ Nanophosphors Through Codoping With Na⁺ and Bi³⁺ Ions

Abstract

Lanthanum phosphate is a well‐known potential host for rare earth activators for phosphor‐converted white LED application. Na+ and Bi3+ codoped Eu3+ activated LaPO4 nanophosphor is successfully synthesized using citrate‐based hydrothermal method at ambient condition and confirmed by XRD, EDS and XPS analysis. The excitation spectra of the sample exhibit sharp f‐f characteristics peak of Eu3+ at 393 nm that is found to be the most dominant. The comparative photoluminescence studies of La1‐xPO4:xEu3+(x = 0.10), La1‐x‐y PO4:xEu3+, yNa+(x = 0.10, y = 0.05), and La1‐x‐y‐zPO4:xEu3+, yNa+, zBi3+ (x = 0.10, y = z = 0.05) reveal a progressive enhancement of the orange emission from Eu3+ as Na+ and (Na+, Bi3+) ions are incorporated into the LaPO4 matrix. The dominance of 5D0‐7F1 magnetic dipole transition contributing a major part of orange luminescence of the nanophosphors and the symmetric site occupancy of Eu3+ was justified from the observed trend of in the Judd–Ofelt intensity parameters. The CIE studies confirm the improvement in color purity of emission from 32.5% to 90.6% due to the presence of Na+ and Bi3+ions.