Enhancement of Upconversion Luminescence in BaMoO4: Er3+/Yb3+ Microcrystals by the Addition of KCl

BaMoO4, co-doped with Er3+, Yb3+ and K+, microcrystals were synthesized by the microwave hydrothermal process. The crystal structure and particle morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The XRD pattern revealed the tetragonal scheelite structure of BaMoO4. In addition, octahedron microcrystals around 0.5-2 mu m were found by SEM analysis. Compositional analysis and the chemical states of the samples were analyzed by X-ray photoelectron spectroscopy (XPS). UV-Vis diffuse reflectance spectra and luminescence properties were also analyzed by UV-Vis diffuse reflectance spectroscopy and photoluminescence spectroscopy. Two strong green emission peaks (526 nm and 554 nm) and one weak red emission peak (661 nm) were observed, which are related to the H-2(11/2) -> I-4(15/2), S-4(3/2) -> I-4(15/2) and F-4(9/2) -> I-4(15/2) transitions of the Er3+ ions, respectively, under 980 nm (CW) laser diode excitation. The green upconversion luminescence intensity was enhanced two times with the KCl addition.