Modification of Local Site Preference for Achieving Tunable Color Emission from Blue to Near-White in Sr3(PO4)2:Dy3+ Phosphor

The color tunability of Sr3(PO4)2:1%Dy3+ phosphor from blue to near white is studied at various annealing conditions. Higher temperature annealing promotes agglomerated rhombohedral (α) phase formation. Experimental and theoretical analysis reveal dopant preference at the low-symmetry Sr(II) site, altering electric (4F9/2→6H13/2) and magnetic (4F9/2→6H15/2) dipole transitions, thereby affecting the yellow-to-blue (Y/B) ratio. The luminescence intensity variation and color tunability are explained based on the local site symmetry and occupation probability of the dopant in the host lattice. An increase in the luminescence intensity up to an annealing temperature of 1200°C, followed by quenching is observed due to the oxygen vacancies. Commission Internationale d'Eclairage (CIE) color coordinates of (0.31, 0.38), Correlated Color Temperature (CCT) of 6341 K, and color purity of 22.57% confirm the potential of Sr3(PO4)2:1%Dy3+ phosphor annealed at (1200°C, 6hrs) for white light generation. A probable photoluminescence mechanism involving 4f→5d→4f transitions in Sr3(PO4)2:1%Dy3+ is proposed.