Sensitizing effect of Nd3+ on Tb3+ activated ZrP2O7 long persistent phosphor materials

The long persistent phosphors of Zr0.97P2O7:0.018Tb3+,0.012Nd3+ with Nd3+ as sensitized ions and Tb3+ as emission centers were synthesized using high temperature solid state reaction. The crystal structure and defects, excitation and emission spectra, decay curves and thermoluminescence (TL) curves of the phosphors were investigated. The synthesized Zr0.97P2O7:0.018Tb3+,0.012Nd3+ is essentially in line with the standard card PDF#49-1079. The emission band with main peak at 548 nm exhibits the characteristic transitions of 5D3-7Fj (j = 5, 4) and 5D3-7Fj (j = 6, 5, 4, 3) of Tb3+. The analysis of excitation and emission spectra shows that there exists the overlap between the emission peaks of Nd3+ at 466 and 485 nm and the excitation of Tb3+ at 443 and 485 nm, and the energy transfer from Nd3+ to Tb3+ plays an important role in the improvement of luminescence properties. The decay curves shows that Zr0.97P2O7:0.018Tb3+,0.012Nd3+ has longer afterglow time than ZrP2O7 and Zr0.982P2O7:0.018Tb3+. Additionally, the TL curves indicate that the trap depth at 0.72 eV in Zr0.97P2O7:0.018Tb3+,0.012Nd3+ is to the benefit of the afterglow time. The possible luminescence mechanism of ZrP2O7:Tb3+,Nd3+ is proposed on the basis of the XPS spectra, EPR spectra, excitation and emission spectra, decay curves, TL curves and the analysis of defect equations.