Synthesis and distinct up-converting behaviors of Er3+, Yb3+ doped LaOF and LaO0.65F1.7 phosphors

Abstract Optical materials composed of tetragonal La 1- x - y Er x Yb y O 0.65 F 1.7 ( x  = 0.005–0.1, y  = 0–0.1) and from tetragonal and trigonal La 0.99 Er 0.005 Yb 0.01 OF were prepared via a solid-state reaction using an excess of NH 4 F flux at 950 or 1050 °C for 2 h. X-ray diffraction patterns of La 1- x - y Er x Yb y O 0.65 F 1.7 and La 0.99 Er 0.005 Yb 0.01 OF were obtained using different molar ratios of the NH 4 F: La(Er,Yb)O 3/2 . The effective spectral conversion properties of Er 3+ -Yb 3+ ions in non-stoichiometric LaO 0.65 F 1.7 host lattices were monitored upon excitation of the samples using a 980 nm diode-laser. By selecting appropriate Er 3+ and/or Yb 3+ concentrations in the LaO 0.65 F 1.7 matrix, up-conversion emission at desired wavelengths in the green to red region of the spectrum was obtained. Furthermore, the mechanism of up-conversion in the nonstoichiometric LaO 0.65 F 1.7 phosphors was described with the help of an energy-level schematic. Up-converted emission spectra and the dependence of the emission intensity on pump power in the La 1- x - y Er x Yb y O 0.65 F 1.7 phosphors were also investigated.