Enhancement of photoluminescence in V-Zn '' defects activated Zn2-delta SiO4-delta persistent phosphor by zinc deficiency

A green long persistent phosphor (LPP) Zn2-delta SiO4-delta with V} Zn defects as emission centers was synthesized using a conventional solid-state reaction. The samples were analyzed by powder X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), photoluminescence (PL), thermoluminescence (TL) techniques and electron paramagnetic resonance (EPR). Rietveld refinement of the XRD patterns confirmed the willemite structure of Zn2SiO4 with minor impurity of SiO2. There is one main emission peak of the green phosphor at 521 nm attributed to V} Zn defects as emission centers. TL curves and the spectra of EPR showed that the defect concentration of phosphors was enhanced by sintering in the reducing atmosphere and Zn deficiency to improve the properties of the phosphor. The long-lasting luminescence of Zn2-delta SiO4-delta was observed for more than 4 h by naked eyes in darkness. The mechanism of photoluminescence of zinc deficiency persistent phosphor was explored.