Souza E L S, Sczancoski J C, Nogueira I C, Almeida M A P, Orlandi M O, Li M S, Luz R A S, Filho M G R, Longo E, Cavalcante L S
PPGQ-CCN-GERATEC, Universidade Estadual do Piauí, Rua: João Cabral, N. 2231, P.O. Box 381, 64002-150 Teresina, PI, Brazil.
DQ-UFSCar, Universidade Federal de São Carlos, P.O. Box 676, São Carlos, SP 13565-905, Brazil.
Ultrason Sonochem. 2017 Sep;38:256-270. doi: 10.1016/j.ultsonch.2017.03.007. Epub 2017 Mar 8.
Copper tungstate (CuWO) crystals were synthesized by the sonochemistry (SC) method, and then, heat treated in a conventional furnace at different temperatures for 1h. The structural evolution, growth mechanism and photoluminescence (PL) properties of these crystals were thoroughly investigated. X-ray diffraction patterns, micro-Raman spectra and Fourier transformed infrared spectra indicated that crystals heat treated and 100°C and 200°C have water molecules in their lattice (copper tungstate dihydrate (CuWO·2HO) with monoclinic structure), when the crystals are calcinated at 300°C have the presence of two phase (CuWO·2HO and CuWO), while the others heat treated at 400°C and 500°C have a single CuWO triclinic structure. Field emission scanning electron microscopy revealed a change in the morphological features of these crystals with the increase of the heat treatment temperature. Transmission electron microscopy (TEM), high resolution-TEM images and selected area electron diffraction were employed to examine the shape, size and structure of these crystals. Ultraviolet-Visible spectra evidenced a decrease of band gap values with the increase of the temperature, which were correlated with the reduction of intermediary energy levels within the band gap. The intense photoluminescence (PL) emission was detected for the sample heat treat at 300°C for 1h, which have a mixture of CuWO·2HO and CuWO phases. Therefore, there is a synergic effect between the intermediary energy levels arising from these two phases during the electronic transitions responsible for PL emissions.
通过声化学（SC）方法合成了钨酸铜（CuWO）晶体，然后在传统炉中于不同温度下热处理1小时。对这些晶体的结构演变、生长机制和光致发光（PL）特性进行了深入研究。X射线衍射图谱、显微拉曼光谱和傅里叶变换红外光谱表明，在100°C和200°C下热处理的晶体在其晶格中有水分子（具有单斜结构的二水合钨酸铜（CuWO·2HO）），当晶体在300°C煅烧时存在两相（CuWO·2HO和CuWO），而在400°C和500°C下热处理的其他晶体具有单一的三斜结构CuWO。场发射扫描电子显微镜显示这些晶体的形态特征随热处理温度的升高而变化。采用透射电子显微镜（TEM）、高分辨率TEM图像和选区电子衍射来研究这些晶体的形状、尺寸和结构。紫外可见光谱表明带隙值随温度升高而降低，这与带隙内中间能级的减少有关。对于在300°C下热处理1小时的样品检测到强烈的光致发光（PL）发射，该样品具有CuWO·2HO和CuWO相的混合物。因此，在负责PL发射的电子跃迁过程中，这两个相产生的中间能级之间存在协同效应。
