Thermal reduction-triggered full-color tuning of Eu3+/Eu2+/Tb3+ co-doped sintered nanoporous Al2O3-SiO2 glass for WLEDs

•A thermal reduction from Eu3+ to Eu2+ upon sintering at air atmosphere was observed in Al2O3-SiO2 glass.•The photoluminescence intensity of the rare earth ions has been increased about 5 times after the densification of nanoporous glass after sintering at 930 °C.•The energy transfer process from Tb3+ to Eu3+ in Al2O3-SiO2 glass was investigated in detail.•The Eu3+/Eu2+/Tb3+ co-doped glass can generate simultaneous triple emission with tunable (from 433 nm to 620 nm) and white light. The development of advanced luminescent materials is highly desirable for developing the energy-efficient lighting technology. However, it is still challenging to achieve stable full-color tuning in the same matrix upon a single-beam light excitation so as to ensure the high color stability and consistency. Herein, Eu3+/Eu2+/Tb3+ co-doped sintered nanoporous glass via the dipping strategy is fabricated, which can emit blue, green and red emissions simultaneously by simply modifying the thermal treatment temperature. This full-color tuning is attributed to the dual roles of the thermal reduction of Eu3+ to Eu2+ in Al2O3-SiO2 glass and simultaneous emissions of Eu3+/Eu2+/Tb3+ activators. The densification of nanoporous glass via sintering could effectively decrease the amount of hydroxyl groups that present in the glass matrix, resulting in 5 times enhancement of the photoluminescence intensity and longer photoluminescence lifetime of rare earth (RE) ions. The thermal reduction of Eu3+ to Eu2+ is due to the reduction environment provided by Al3+ ions in the Al2O3-SiO2 glass. The energy transfer (ET) from Eu2+ to Tb3+, Eu2+ to Eu3+ and Tb3+ to Eu3+ have been investigated in detail. Based on the ET mechanism, rational PL spectra design was demonstrated by varying the concentration of Eu3+ ions in solution. The Color Correlated Temperature (CCT) and the Color Rendered Index (CRI) values of the white light emission glass are 7420 K (Cold-white emission) and 80.85, the temperature dependent photoluminescence (TDPL) analysis reflects the white light emission glass possesses high thermal stability and excellent thermal restorability. This facile fabrication and full-color tuning of Eu3+/Eu2+/Tb3+ co-doped sintered nanoporous Al2O3-SiO2 glass may provide a novel luminescent material for white-light emitting diodes (WLEDs) application.