Synthesis and luminescence characterization of Pr~(3+) doped Sr_(1.5)Ca_(0.5)SiO_4 phosphor

摘要

Luminescence properties of Pr~(3+) activated Sr_(1.5)Ca_(0.5)SiO_4 phosphors synthesized by solid state reaction method are reported in this work. Blue, orange red and red emissions were observed in the Pr~(3+) doped sample under 444 nm excitation and these emissions are assigned as ~3P_0 → ~3H_4, ~3P_0 → ~3H_6 and ~3P_0 → ~3F_4 transitions. The emission intensity shows a maximum corresponding to the 0.5 wt% Pr~(3+) ion. The decay analysis was done for 0.05 and 0.5 wt% Pr~(3+) doped samples for the transition ~3P_0 → ~3H_6. The life times of 0.05 and 0.5 wt% Pr~(3+) doped samples were calculated by fitting to exponential and nonexponential curve respectively, and are found to be 156 and 105 μs respectively. The non-exponential behaviour arises due to the statistical distribution of the distances between the ground state Pr~(3+) ions and excited state Pr~(3+) ions, which cause the inhomogeneous energy transfer rate. The XRD spectrum confirmed the triclinic phase of the prepared phosphors. The compositions of the samples were determined by the energy dispersive X-ray spectra. From the SEM images it is observed that the particles are agglomerated and are irregularly shaped. IR absorption bands were assigned to different vibrational modes. The well resolved peaks shown in the absorption spectra are identical to the excitation spectra of the phosphor samples. Pr~(3+) activated Sr_(1.5)Ca_(0.5)SiO_4 phosphors can be efficiently excited with 444 nm irradiation and emit multicolour visible emissions. From the CIE diagram it can be seen that the prepared phosphor samples give yellowish-green emission.