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 Oi is easily formed by the lattice oxygen (O1) with increasing Sr2+ content and air atmosphere may also provide Oi(Oi=1/2O2). Besides, emission intensities of samples regularly changed by accommodating more Oi in air. By selecting proper excitation energy (276/355 nm), emission occurred from different Oi 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 Oi, which was located in the interior of [AlO4] six-member rings and the capacity of accommodating Oi 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.