Variation of crystal structure and defect luminescence in Ca3-xSrxAl2O6 phosphors

Ca3-xSrxAl2O6(x=0, 1.07, 1.88, 1.98, 3) phosphors were prepared through solid state reaction route under different atmospheres and two kinds of oxygen-defects were identified in Ca3-xSrxAl2O6 by means of X-ray photoelectron and electron spin-resonance spectra. Their defect luminescence behavior was discussed based on photoluminescence spectra as well as the calculation of bond volume polarizability of chemical bonds. Interstitials oxygen O-i is easily formed by the lattice oxygen (O1) with increasing Sr2+ content and air atmosphere may also provide O-i(O-i=1/2O(2)). Besides, emission intensities of samples regularly changed by accommodating more O-i in air. By selecting proper excitation energy (276/355 nm), emission occurred from different O-i defect centers, with Spectral regions from 350 nm to 600 nm. Analysis suggested that the tunable emission characteristic at different excitation energies was linked with abnormal O-i which was located in the interior of [AlO4] six-member rings and the capacity of accommodating O-i is related to the size of six-member rings. Based on the theoretical and experimental results, a model was proposed to explain the mechanisms related to emission tunability accordingly. This research may help elucidate emission induced by an oxygen defects system.