Fluorescence kinetics for upconversion enhancement of Er/Yb doped oxyfluoride glass ceramics by K ions doping.

This study develops an oxyfluoride GCs embedded with β-PbF:4Yb/1Er/xK NCs by conventional melting-quenching method. Based on XRD and EDS line scanning data, it was inferred that Er/Yb and K ions were co-doped in the β-PbF lattice by substituting Pb ions. Compared with K ions free doping GCs, in β-PbF:4Yb/1Er/xK GCs, the synergistic substitution of Pb ions by K and Er/Yb into the β-PbF lattice not only effectively eliminates the charge imbalance defects caused by single doping of Er/Yb ions, but also causes lattice distortion around Er/Yb. It is precisely the elimination of lattice defects and lattice distortion caused by K ion doping that leads to a significant increase in upconversion luminescence (UCL) intensity of β-PbF:4Yb/1Er/xK GCs. Compared with free doping K ions GCs, β-PbF:4Yb/1Er/7.5K GCs presents the maximum UCL intensity and the maximum enhancement is 42.7, 109.5, 32.2 and 42.4 for violet emission, blue emission, green emission and red emission, respectively. The corresponding energy transfer mechanism of UCL was addressed, and the pivotal roles of charge compensation and lattice distortion induced by K ions in radiative transitions of Er ions energy levels were revealed through rate equations analysis. Based on significantly enhanced violet UCL, the temperature-sensing behavior based on the FIR of the thermally coupled levels (TCLs):G/H is investigated over a temperature range from 300 to 500 K. The highest relative thermal sensitivity, 1.47 % K, was found at 300 K for β-PbF:4Yb/1Er/7.5K GCs. The obtained results confirm the high application potential of this GCs for UCL device such as solid state lighting and fluorescence thermometers.