Characterization of the photoluminescent properties of MWO₄ (M = Zn and Ca) synthesized by spray pyrolysis

Full text: Tungstates are an important material class because it presents high stability, low cost and eco-friendliness, besides presenting applications in catalysis, optics, magnetism and electrochemistry [1]. MWO₄ (A= Zn and Ca) powders were synthesized, in a one-step, by the ultrasonic spray pyrolysis method. Powders were characterized by X-ray diffraction (XRD), scanning electronic microscopy (FESEM) and UV-visible and Photoluminescence (PL) spectroscopies. The XRD patterns showed that the ZnWO₄ and CaWO₄ samples displayed pure monoclinic and tetragonal structures, respectively. The FESEM images showed that the ZnWO₄ and CaWO₄ particles present the spherical morphology, predominantly. The gap energies vary between 3.88 eV and 3.99 eV, being influenced by the degree of structural order-disorder. The PL emission spectra of the samples showed a broad band behavior with emission intensity predominant in the blue green region and of a lower intensity in the orange-red region. The chromaticity coordinates x and y showed that the ZnWO₄ and CaWO₄ exhibited emission in white (CCT ~ 7600 K). References: [1] Pereira, Paula Fabiana dos Santos et al. ZnWO₄ nanocrystals: synthesis, morphology, photoluminescence and photocatalytic properties. Physical Chemistry Chemical Physics, v. 20, n. 3, p. 1923-1937, 2018. (author)