Photoluminescence and defect centers in near violet emitting Pb2+ doped CaYAl3O7 phosphors obtained by urea-nitrate auto combustion synthesis

Abstract

A series of CaYAl3O7 phosphors doped with different concentrations of Pb2+ were prepared by an auto solution combustion route. The structure, luminescence, and electron paramagnetic resonance (EPR) spectra were analysed. The X-ray diffraction (XRD) patterns identify the tetragonal phase formation of CaYAl3O7 with a crystallite size in a range of 37–42 nm. The scanning electron microscope (SEM) images were captured to study the surface morphology of the prepared samples. The emission spectra for the prepared phosphors exhibit a wide emission band centered at 362 nm under 270 nm excitation. Un-doped and Pb2+ doped CaYAl3O7 phosphor exhibit an EPR spectrum which arises from two noticeable defect centers. Center I with a g-value equal to 1.96 and a relatively broad line width is temporarily defined to an F+ - center (an electron trapped at an anion vacancy). Center II with g = 2.0 is also ascribed to an F+ - center.