An Efficient Construction Model of Multi-Fluorescence Morphologies in Oxyfluoride Matrix

As the most common up-conversion (UC) activation center now, Er3+ can emit the blue, green and red light under the excitation of 980 nm. It has important meaning how to manipulate the emission wavelength in practical application. In our work, a series of excellent UC luminescence materials Y6O5F8: M3+ (M = Yb, Er, and Fe) are synthesized by the hydrothermal method. Under the condition of different pH, the prepared precursors exhibited different phases of YF3 and Y(OH)1·63F1.37 and various morphologies. The hydrogen bond guides a regular crystal growth process. With the change of pH, OH group could be selectively introduced into the host during this different crystal growth process. The structure change is likely to decrease the rigidity of this lattice and adjusted the cut-off phonon energies, and further influence the f-f transition of Er3+, selectively forming red emission in Y6O5F8: Yb3+, Er3+. The intensity of red UC luminescence is enhanced by 22 times via Fe3+ co-doping into the Y6O5F8: Yb3+, Er3+ crystalline lattice. The introduction of transition metal ions Fe3+, produces an excellent energy transfer from <2F7/2, 4T1g> (Yb3+-Fe3+ dimer) to energy levels of Er3+ as well as the distortion of the crystalline field symmetry. In addition to the enhancing luminescence effect, Fe ions also introduce magnetism from the hysteresis loop curve. The temperature-dependent UC emission of Y6O5F8: Yb3+, Er3+, Fe3+ display significant thermal coupling occurs with a higher absolute sensitivity. Based on this, the anti-fake and temperature-sensitive luminescent applications of this material are investigated in detail.