Correlation of oxygen defects variations to band gap changes in luminescence properties of SrZnO2: 0.02 Eu3+ phosphors

•Divalent europium ions don’t exist stably in sample prepared in air.•Absorption spectra had red-shift with the increase of oxygen defects inside samples.•Oxygen defects can diminish the band gap of SrZnO2: 0.02 Eu3+ phosphor.•Photoluminescence (PL) spectra of samples depend greatly on their band gap widths.•Effect of oxygen vacancies on the PL spectra of samples is stronger than that of Oi. The SrZnO2: 0.02 Eu3+ phosphors were prepared by conventional solid-state reactions in O2, air, N2 and Ar, respectively. X-ray photoelectron spectroscopy analyses show that the concentration of oxygen defects in samples change obviously under different atmospheres. From the data collected by UV–vis diffuse reflectance spectroscopy and the fluorescence spectra, it is found that Vӧ and oxygen interstitials can diminish band gaps of samples, promoting an increase in photoluminescence intensities of samples on the based of host-sensitized luminescence effect, in which the effect of oxygen vacancies is stronger than that of oxygen interstitials. The mechanism of band gap narrowing has been explained in detail.