Unravelling the effect of interstitial oxygen on the photoluminescence of Ce3+-doped Ca2BO3Cl and Ca3(BO3)2

Ce3+-doped Ca2BO3Cl and Ca3(BO3)2 are presented as promising phosphors for solid-state white light illumination, display, phototherapy, etc. Herein, we combined experimental and first-principles calculations to study the photoluminescence properties of Ce3+-doped Ca2BO3Cl and Ca3(BO3)2 under different preparation environment. The results show that the co-doped Na + ions have little effect on the luminescence of Ce3+ ions doped Ca2BO3Cl and Ca3(BO3)2. However, the luminous intensity of Ce3+/Na+ ions co-doped Ca2BO3Cl greatly decreased with increasing oxidizing atmosphere. When sintering at 800 °C in air, the luminescence intensity was more than 10 times lower than that in a reducing atmosphere (5 % H2 + 95 % N2), whereas the luminescence intensity of Ce3+-doped Ca3(BO3)2 hardly changed. First-principles calculations revealed that, within an enhanced oxidizing atmosphere, the formation energy of interstitial oxygen (Oi) in Ca2BO3Cl:Ce3+,Na+ decreased from 2.84 to 0.31 eV, whereas in Ca3(BO3)2:Ce3+, it decreased from 2.11 to 1.51 eV. The small formation energy (0.31 eV) of interstitial oxygen (Oi) in an oxidation atmosphere may lead to the formation of interstitial oxygen defects in Ca2BO3Cl:Ce3+,Na+, which may result in the luminescence quenching of Ce3+ ions in Ca2BO3Cl:Ce3+,Na+ ((Ce3+)∗+O0→Ce4++O1−) and cause a decrease in the luminescence intensity. The study of the difference in resistance to oxidation between Ce3+-doped Ca2BO3Cl and Ca3(BO3)2 is highly important for further improving current luminescent materials and developing new functional materials. •The luminescence quenching phenomenon of Ca2BO3Cl:Ce3+/Na+ is discovered.•Main defects in Ca2BO3Cl:Ce3+/Na+ and Ca3(BO3)2:Ce3+ are identified by calculation.•The effect of interstitial oxygen on the photoluminescence is revealed.