PROPRIEDADES TÉRMICAS DO Bi2WO6 EM DUPLA CAMADA: UMA INVESTIGAÇÃO IN SITU POR ESPECTROSCOPIA RAMAN E DIFRAÇÃO DE RAIOS X

Abstract

This work presents an investigation of double-layer bismuth tungstate (Bi2WO6 2D) as a function of temperature. At room temperature, Bi2WO6 exhibits ferroelectric behavior with a high Curie temperature (1,223 K), and recent studies have demonstrated its significant applicability in photoluminescent devices, photocatalytic processes, and electronic components. In this study, the synthesis of double-layer Bi2WO6 was carried out via a hydrothermal method assisted by cetyltrimethylammonium bromide (CTAB). Structural and vibrational characterizations were performed using powder X ray diffraction (XRD) and Raman scattering, respectively. Morphological analysis was conducted through Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), and Transmission Electron Microscopy (TEM). Additionally, the influence of temperature on the structural properties of double-layer Bi2WO6 was evaluated in the range of 10 K to 940 K. The synthesized material exhibited an orthorhombic crystal structure with space group P21ab, organized into alternating perovskite-like [WO4] 2- layers and fluorite-like [Bi2O2] 2+ layers. Morphological analysis revealed a plate-like structure with an average thickness of approximately 1.50 nm, corresponding to a single unit cell along the [001] direction, as evidenced by AFM and SEM images. Furthermore, TEM analysis indicated that the material exhibits a polycrystalline nature. The structural data obtained from temperature-dependent XRD and Raman spectroscopy revealed that the double-layer Bi2WO6 undergoes morphological instability at temperatures above 620 K. Variations in lattice parameters, reduction in full width at half Maximum (FWHM), and significant changes in the Raman spectra were observed, indicating the degradation of the two-dimensional structure and a transition toward the bulk form of the material.