GdPO4:Sm3+ phosphor: Optimization of calcination temperature and doping concentration and fluorescence and magnetic properties

Nano-phosphor precursors were synthesized with GdPO4 as the matrix and Sm3+ as the activator using the hydrothermal synthesis method. The precursors were calcinated at 800, 900, 1 000, 1 100, and 1 200 degrees C respectively, thus obtaining GdPO4:Sm3+ phosphors. Firstly, the optimal calcination temperature of GdPO4:Sm3+ was optimized. Then the effect of Sm3+ doping amount on the fluorescence properties of GdPO4:Sm3+ was studied. The high-temperature fluorescence and magnetic properties of the best product were studied in detail. The crystal structure, morphology, luminescence, and magnetic properties of the phosphors were characterized using an X-ray diffractometer (XRD), scanning electron microscope (SEM), magnetometer, and fluorescence spectrophotometer (FL). The results indicate that the crystal structure of phosphors was changed from the precursor GdPO4 center dot H2O:Sm3+ in the hexagonal crystal system to GdPO4:Sm3+ in the monoclinic crystal system. The morphology was changed from nanorods to like-sphere particles. The luminous intensity and phosphorescence lifetime of the phosphors attained their highest levels when the calcination temperature was 1 000 degrees C and the Sm3+ doping concentration was 2%. The type of energy transferred between Sm3+ in GdPO4:2%Sm3+ was electric dipole-electric dipole interaction, and the critical distance of energy transfer was about 1.646-1.884 nm. The optimal product GdPO4:2%Sm3+ had excellent thermal stability, with the thermal quenching activation energy as -0.157 eV. Moreover, it had good paramagnetism, with a mass susceptibility of 1.22x10(-4) emu center dot g(-1)center dot Oe(-1).