Excellent upconversion luminescence intensity in Er3+/Yb3+/Mo4+ triple-doped BiTa7O19 phosphors

Abstract

BiTa7O19:Er3+/Yb3+/Mo4+ phosphors with excellent upconversion luminescence (UCL) intensity were synthesized by high temperature solid state method. The crystal structure, grain morphology and valence states of molybdenum ions were determined by X-ray diffraction (XRD), field emission scan electronic microscopy (FESEM) and X-ray photoelectron spectroscopy (XPS) technologies, respectively, and the UCL properties were studied by spectroscopy under 980 nm laser excitation. The green UCL intensity of BiTa7O19:0.1Er3+/0.4Yb3+/0.4Mo4+ is 1.66 times higher than that of commercial NaYF4:Er3+/Yb3+ under 980 nm laser excitation with 18.09 W/cm2. The UCL intensity of BiTa7O19:Er3+/Yb3+ phosphors increased first and then decreased with the increase of 980 nm laser excitation power density (0.38–56.69 W/cm2), while the UCL intensity of BiTa7O19:Er3+/Yb3+/Mo4+ phosphors can keep increasing with the increase of excitation power density. Based upon the luminescence intensity ratio (LIR) technique, the maximum absolute sensitivity (SA) is 0.01046 K−1 at 401 K. The experiment proved that BiTa7O19:Er3+/Yb3+/Mo4+ phosphors had strong acid and alkali resistance compared with NaYF4:Er3+/Yb3+. It indicates that BiTa7O19:Er3+/Yb3+/Mo4+ can replace NaYF4:Er3+/Yb3+ to be applied as luminescence imaging and temperature sensors in complex environments under high 980 nm laser excitation power density.