Morphology and Blue Photoluminescence Emission of PbMoO₄ Processed in Conventional Hydrothermal

Abstract

PbMoO 4 micro-octahedrons were prepared by the coprecipitation method at room temperature without the presence of surfactants and processed in a conventional hydrothermal at different temperatures (from 60 to 120 °C) for 10 min. These micro-octahedrons were structurally characterized by X-ray diffraction (XRD) and micro-Raman (MR) spectroscopy, and its morphology was investigated by field-emission gun scanning electron microscopy (FEG-SEM). The optical properties were analyzed by ultraviolet−visible (UV−vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns and MR spectra confirmed that the PbMoO 4 micro-octahedrons are characterized by a scheelite-type tetragonal structure. FEG-SEM micrographs points out that these structures present a polydisperse particle size distribution in consequence of a predominant growth mechanism via aggregation of particles. In addition, it was observed that the hydrothermal conditions favored a spontaneous formation of micro-octahedrons interconnected along a common crystallographic orientation (oriented-attachment), resulting in self-organized structures. An intense blue PL emission at room temperature was observed in these micro-octahedrons when they were excited with a 350 nm wavelength. The origin of the PL emissions as well as its intensity variations are explained by means of a model based on both distorted [MoO 4 ] and [PbO 8 ] clusters into the lattice.