Cooperative-luminescence-assisted single-band upconverted red emission in Er3+ and Yb3+ co-doped MgAlON transparent ceramic

Although single-band emission upconversion fluorescence, which is particularly important in sensors, biomedical and imaging applications, has been extensively investigated in nanoparticles using energy transfer engineering, it is still difficult to be achieved in transparent ceramics. Herein, the MgAlON: Er3+/Yb3+ transparent ceramics with functionalized grain boundaries were successfully fabricated. Lanthanide ions were investigated to highly enrich at the MgAlON grain boundaries, resulting in novel fluorescent properties. Upon 980 nm laser excitation, the sample emitted temperature and excitation power-independent single-band red upconverted fluorescence with a red-to-green fluorescence intensity ratio of similar to 25. The new mechanism of Yb3+-Yb3+ cooperative fluorescence-assisted energy transfer, which is responsible for the single-band feature, was elucidated. Moreover, the upconverted fluorescence chromaticity can be modified by the excitation wavelength, relying on the existence of the cooperative fluorescence level and its related energy transfer mechanism. This work reveals the potential of grain boundary functionalization of transparent ceramics in energy transfer engineering.