Blue to Red Emission Tunable Bi³⁺ co-doped YPO₄:Eu³⁺: Host Emission and Phase Change

Bi³⁺(0, 1, 3, 5, 7, 10, 12 and 15 at.%) co-doped YPO₄:Eu³⁺ have been hydrothermally synthesized. Bi³⁺ (x ≥ 1 at.%) co-doping in YPO₄:Eu³⁺ renders mixed crystalline phase of tetragonal to hexagonal. Pure tetragonal phase of Bi³⁺ co-doped YPO₄:Eu³⁺ could be achieved upon annealing at 900 °C. The luminescence intensity is improved significantly upon annealing at 900 °C. This is due to the reduction of quenching pathways such as water molecules, dangling bonds, etc. The probability of magnetic dipole and electric dipole transitions is observed to be altered. As-prepared samples show near blue emission, while 900 °C annealed samples exhibit red emission, which could be a potential candidate for display, sensing and biological labelling, etc.