Hydrothermal synthesis of quasi-monodisperse AWO4 (A = Ca, Sr, and Ba) microspheres

Abstract

In this study, quasi-monodisperse AWO4 (A = Ca, Sr, and Ba) microspheres were fabricated by a facile hydrothermal route at 180 °C for 8 h in the presence of citric acid. The as-synthesized AWO4 powders were characterized by X-ray powder diffraction (XRD), scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy. The XRD results revealed that the hydrothermally formed AWO4 powders presented a scheelite-type tetragonal structure, and the formation of a secondary phase was not observed. The SEM and TEM observations demonstrated that the AWO4 powders with uniform sphere-like morphologies could be hydrothermally obtained at 180 °C for 8 h without the use of surfactants. The growth process of quasi-monodisperse BaWO4 microspheres, as a representative of AWO4, was investigated as a function of hydrothermal processing time, and a possible formation mechanism was proposed. The room temperature photoluminescence properties of AWO4 powders were studied using an excitation wavelength of 350 nm. The positions of the PL emission peaks were not considerably altered, implying that the energy band gap relating to the blue emission was not much affected by the variation in chemical composition of AWO4 (A = Ca, Sr, and Ba) microspheres. The obtained quasi-monodisperse AWO4 microspheres will be potential candidates for a broad range of technological applications, as phosphors, luminescent materials, photocatalysts, etc.