Electronic structure, growth mechanism and photoluminescence of CaWO4 crystals

被引:202
作者
Cavalcante, L. S. [1 ]
Longo, V. M. [1 ]
Sczancoski, J. C. [1 ]
Almeida, M. A. P. [2 ]
Batista, A. A. [2 ]
Varela, J. A. [1 ]
Orlandi, M. O. [1 ]
Longo, E. [1 ]
Li, M. Siu [3 ]
机构
[1] Univ Estadual Paulista, BR-14801907 Araraquara, SP, Brazil
[2] Univ Fed Sao Carlos, BR-13565905 Sao Carlos, SP, Brazil
[3] IFSC Univ Sao Paulo, BR-13560970 Sao Carlos, SP, Brazil
基金
巴西圣保罗研究基金会;
关键词
MICROWAVE DIELECTRIC-PROPERTIES; RIETVELD TEXTURE ANALYSIS; RAMAN-SPECTROSCOPY; LUMINESCENCE PROPERTIES; HYDROTHERMAL SYNTHESIS; OPTICAL-ABSORPTION; ASSISTED SYNTHESIS; METAL TUNGSTATES; BAWO4; CRYSTALS; IR-SPECTRA;
D O I
10.1039/c1ce05977g
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
In this paper, aggregated CaWO4 micro-and nanocrystals were synthesized by the co-precipitation method and processed under microwave-assisted hydrothermal/solvothermal conditions (160 degrees C for 30 min). According to the X-ray patterns, all crystals exhibited only the scheelite-type tetragonal structure. The data obtained by the Rietveld refinements revealed that the oxygen atoms occupy different positions in the [WO4] clusters, suggesting the presence of lattice distortions. The crystal shapes as well as its crystallographic orientations were identified by field-emission scanning electron microscopy and high-resolution transmission electron microcopy. Electronic structures of these crystals were evaluated by the first-principles quantum mechanical calculations based on the density functional theory in the B3LYP level. A good correlation was found between the experimental and theoretical Raman and infrared-active modes. A crystal growth mechanism was proposed to explain the morphological evolution. The ultraviolet-visible absorption spectra indicated the existence of intermediary energy levels within the band gap. The highest blue photoluminescence emission, lifetime and quantum yield were observed for the nanocrystals processed in the microwave-assisted solvothermal method.
引用
收藏
页码:853 / 868
页数:16
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