Artigo
Rietveld refinement, cluster modelling, growth mechanism and photoluminescence properties of CaWO4: Eu3+ microcrystals
Registro en:
Crystengcomm. Cambridge: Royal Soc Chemistry, v. 17, n. 7, p. 1654-1666, 2015.
1466-8033
10.1039/c4ce02279c
WOS:000349309700023
Autor
Goncalves, R. F.
Cavalcante, L. S.
Nogueira, I. C.
Longo, Elson [UNESP]
Godinho, M. J. [UNESP]
Sczancoski, J. C. [UNESP]
Mastelaro, V. R.
Pinatti, I. M.
Rosa, I. L. V.
Marques, A. P. A.
Resumen
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. Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) National Laboratory of Synchrotron Light Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) UNIFESP (Universidade Federal de São Paulo), Rua Prof. Artur Riedel, 275, Diadema, Brazil Departamento de Química, UESPI, CCN, Rua João Cabral, P.O. Box 2231, Teresina-PI, Brazil IFMA (Instituto Federal de Educação), Ciência e Tecnologia do Maranhão, PPGEM, São Luís, Brazil Departamento de Química, CAC/UFG (Universidade Federal de Goiás), Catalão, Brazil IFSC, Universidade de São Paulo, P.O. Box 369, São Carlos, Brazil CDMF-DQ, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, Brazil Universidade Estadual Paulista, LIEC IQ, BR-14801907 Araraquara, SP, Brazil FAPESP: 2013/07296-2 CNPq: 304531/2013-8 National Laboratory of Synchrotron Light: D04B-XAFS1-11883