Joshi Upendra A, Yoon Songhak, Baik Sunggi, Lee Jae Sung
Department of Chemical Engineering and School of Environmental Science and Engineering, Pohang University of Science and Technology, San 31 Hyoja-dong, Pohang 790-784, Korea.
J Phys Chem B. 2006 Jun 29;110(25):12249-56. doi: 10.1021/jp0600110.
Barium titanate nanowires synthesized with a surfactant-free hydrothermal method have been characterized by various techniques such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), synchrotron X-ray diffraction, X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The TEM and SEM analyses show the uniform cylindrical nanowires. The Rietveld refinement with synchrotron X-ray powder diffraction showed that the lattice parameters of cubic and tetragonal phases were a (= b = c) = 4.0134 A and a (= b) = 3.9998 A, c = 4.0303 A, respectively. The final weighted R-factor, R(wp), was 6.75% and the goodness of fit indicator was 1.30. The mass fraction of tetragonal and cubic phases based on the refined scale factor for the two phases were 98.4% and 1.6%, respectively, which clearly show the nanowires are tetragonal. The XPS analysis has shown that as-obtained BaTiO3 nanowires were phase pure. The Raman spectra confirm the tetragonal phase of the BaTiO3 nanowires. The dielectric constant measurement shows the shift in the transition temperature (Tc = 105 degrees C) compared to the bulk transition temperature (Tc = 132 degrees C). The dielectric constant at Tc was 174 measured at 1 kHz frequency.
采用无表面活性剂水热法合成的钛酸钡纳米线已通过多种技术进行了表征，如透射电子显微镜（TEM）、扫描电子显微镜（SEM）、同步辐射X射线衍射、X射线光电子能谱（XPS）和拉曼光谱。TEM和SEM分析显示出均匀的圆柱形纳米线。同步辐射X射线粉末衍射的Rietveld精修表明，立方相和四方相的晶格参数分别为a（=b=c）=4.0134 Å和a（=b）=3.9998 Å，c = 4.0303 Å。最终加权R因子R（wp）为6.75%，拟合优度指标为1.30。基于两相精修比例因子的四方相和立方相的质量分数分别为98.4%和1.6%，这清楚地表明纳米线为四方相。XPS分析表明，所制备的BaTiO3纳米线为纯相。拉曼光谱证实了BaTiO3纳米线的四方相。介电常数测量表明，与体相转变温度（Tc = 132℃）相比，转变温度发生了偏移（Tc = 105℃）。在1 kHz频率下测得的Tc处的介电常数为174。
