Effect of Zn2+ ions on the structure, morphology and optical properties of CaWO4 microcrystals

Author(s)

Almeida, M. A. P. ^[1] ; Lima, J. R. O. ^[1] ; Morila-Santos, C. ^[2] ; Lisboa Filho, P. N. ^[3] ; Siu Li, M. ^[4] ; Longo, E. ^[5] ; Cavalcante, L. S. ^[6]

Affiliation

^[1] Univ Fed Maranhao, Coordenacao Ciencias & Tecnol, BR-65080805 Sao Luis, MA - Brazil

^[2] Univ Fed Ceara, Dept Fis, BR-60455760 Fortaleza, Ceara - Brazil

^[3] UNESP Univ Estadual Paulista, MAv DF, BR-17033360 Bauru, SP - Brazil

^[4] Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP - Brazil

^[5] UNESP Univ Estadual Paulista, Inst Quim, BR-14800900 Araraquara, SP - Brazil

^[6] Univ Estadual Piaui, CCN DQ GERATEC, BR-64002150 Teresina, PI - Brazil

• Document type: Journal article
• Source: Journal of Sol-Gel Science and Technology; v. 72, n. 3, p. 648-654, DEC 2014.
• Web of Science Citations: 1

Abstract

The effect of zinc ions (Zn2+) on the structure, morphology and optical properties of (Ca1-x Zn (x) )WO4 microcrystals with (x = 0, 0.01, 0.02, and 0.03) obtained by the microwave-hydrothermal method at 170 A degrees C for 1 h is reported in this letter. These microcrystals were characterized by X-ray diffraction (XRD), Rietveld refinement, energy dispersive X-rays spectroscopy (EDXS) and field emission scanning electron microscopy (FE-SEM) images. The optical properties were investigated by ultraviolet-visible (UV-Vis) diffuse reflectance spectroscopy and photoluminescence (PL) measurements. XRD patterns and Rietveld refinement data indicated that all the (Ca1-x Zn (x) )WO4 microcrystals present a tetragonal structure and a reduction of lattice parameters and unit cell volume occurs with the increase of Zn2+. EDXS data confirms that the elemental chemical composition was achieved for (Ca1-x Zn (x) )WO4 microcrystals. FE-SEM images showed that the replacement of Ca2+ by the Zn2+ promotes a reduction of average crystals size and considerable changes in crystal shape starting from dumbbell-like to decorative ball-like (Ca1-x Zn (x) )WO4 microcrystals. UV-Vis spectra evidenced a small increase in optical band gap values (from 5.72 to 5.76 eV). Finally, PL emission of (Ca1-x Zn (x) )WO4 microcrystals was improved until x = 0.02 due to the presence of defects at medium range and new intermediate electronic levels in the band gap associated to the Zn2+ content. (AU)

• FAPESP's process: 09/50303-4 - Optical and photocatalytic properties of ZnMoO4 and ZnWO4
• Grantee: Laécio Santos Cavalcante
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 12/18597-0 - Investigation of photoluminescent, photocatalytic and bactericide properties of (Ca1-xZnx)WO4 and (Ca1-xAg2x)WO4
• Grantee: Marcio Aurélio Pinheiro Almeida
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 13/07296-2 - CDMF - Center for the Development of Functional Materials
• Grantee: Elson Longo da Silva
• Support Opportunities: Research Grants - Research, Innovation and Dissemination Centers - RIDC