Effects of pH and Sm3+ doping on the structure, morphology and luminescence properties of BiPO4:Sm3+ phosphors prepared by hydrothermal method

BiPO4 and Bi1−xPO4:xSm3+ phosphors were successfully synthesized by a simple hydrothermal method at different pH. The influences of pH and Sm3+ doping on the structure, morphology and luminescence properties of BiPO4:Sm3+ were investigated systematically. X-ray diffraction (XRD) and field emission scanning electron microscope (FE-SEM) results reveal that a phase transition from low temperature monoclinic phase (LTMP) to hexagonal phase (HP) occurs with increasing pH and Sm3+ doping, accompanied by a morphology transition from octahedron-like to short rod-like. At pH 0.5, the crystal structure and morphology of the Bi1−xPO4:xSm3+ remain the same with Sm3+ doping, indicating that the structural transition induced by Sm3+ doping can be suppressed under strong acid condition. The photoluminescence (PL) spectra suggest that the optimal emission intensity of BiPO4:Sm3+ appears at pH 0.5, which may be attributed to the single LTMP. The concentration quenching occurs when x is beyond 0.11, which is ascribed to dipole-dipole interaction.