Rietveld refinement, cluster modelling, growth mechanism and photoluminescence properties of CaWO4:Eu3+ microcrystals

Author(s)

Goncalves, R. F. ^[1] ; Cavalcante, L. S. ^[2] ; Nogueira, I. C. ^[3] ; Longo, E. ^[4] ; Godinho, M. J. ^{[4, 5]} ; Sczancoski, J. C. ^[4] ; Mastelaro, V. R. ^[6] ; Pinatti, I. M. ^[7] ; Rosa, I. L. V. ^[7] ; Marques, A. P. A. ^[1]

Affiliation

^[1] UNIFESP Univ Fed Sao Paulo, BR-09972270 Diadema, SP - Brazil

^[2] Univ Estadual Piaui, CCN, Dept Quim, BR-64002150 Teresina, PI - Brazil

^[3] PPGEM, IFMA Inst Fed Educ Ciencia & Tecnol Maranhao, Sao Luis, MA - Brazil

^[4] Univ Estadual Paulista, LIEC IQ, BR-14801907 Araraquara, SP - Brazil

^[5] UFG, CAC, Dept Quim, BR-75704020 Catalao, Go - Brazil

^[6] Univ Sao Paulo, IFSC, BR-13560970 Sao Carlos, SP - Brazil

^[7] Univ Fed Sao Carlos, CDMF DQ, BR-13565905 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: CrystEngComm; v. 17, n. 7, p. 1654-1666, 2015.
• Web of Science Citations: 34

Abstract

CaWO4:Eu3+ microcrystals (with 0, 1, 2 and 4 mol% Eu3+) were synthesized by a co-precipitation (CP) method and grown in a microwave-assisted hydrothermal (MAH) system at 130 degrees C for 30 min. X-ray diffraction (XRD), Rietveld refinement, X-ray absorption near edge spectroscopy (XANES), Fourier-transform Raman (FT-Raman) and Fourier-transform infrared (FT-IR) spectroscopy indicated that all of the microcrystals have a scheelite-type tetragonal structure without deleterious phases. Structural refinement data were employed to model the {[}CaO8], {[}EuO8] and {[}WO4] clusters. XANES spectra confirmed that the presence of deltahedral {[}EuO8] clusters promotes small distortions of neighbouring tetrahedral {[}WO4] clusters in a global tetragonal lattice. Field emission scanning electron microcopy (FE-SEM) images revealed that the replacement of Ca2+ by Eu3+ ions changed the particles' shapes, resulting in the different morphologies of the microcrystals. UV-vis diffuse reflectance spectra indicated a reduction in the optical band gap with the replacement of Ca2+ by Eu3+ ions. The photoluminescence (PL) properties of the Eu3+ ions in CaWO4 were studied as well as the chromaticity coordinates and lifetimes of these compounds. (AU)

• 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