Raman scattering, electronic, and ferroelectric properties of Nd modified Bi4Ti3O12 nanotube arrays
ABSTRACT Neodymium-modified bismuth titanate, Bi 4- x Nd x Ti 3 O 12 (BNdT), nanotube arrays were fabricated by sol-gel method utilizing experimentally prepared porous anodic aluminum oxide (AAO) templates with pore diameters of about 200 nm and 100 nm, respectively. The as-prepared nanotube arrays exhibit orthorhombic perovskite polycrystalline structure of BNdT, which have outer diameters of about 200 and 100 nm, corresponding to the pores diameters of the AAO templates employed, and with wall thicknesses of about 9.7 nm and 12 nm, respectively. The phonon vibration modes corresponding to the Bi atoms in the Bi 2 O 2 layers weaken and broaden with increasing Nd content. The changes of Raman internal modes originated from the vibrations of atoms inside the TiO 6 octahedral indicate the increase in octahedron tilting and structural distortion. The leakage current and polarization-electric field response curves of BNdT nanotube arrays were measured, and the hysteresis loop illustrates a good ferroelectric property of as-prepared BNdT nanotube array at room temperature. The dielectric constant and dissipation factor were measured in the frequency region from 1 kHz to 1 MHz indicating polarization relaxation phenomenon.
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ABSTRACT: A simple method of fabricating Co-containing anodic aluminum oxide films for multifunctional anti-counterfeit technology is reported. The films display highly saturated colors after being synthesized by an ac electrodeposition method. Tunable color in the films is obtained by adjusting anodization time, and can be adjusted across the entire visible range. Magnetic measurements indicate that such colored composite films show excellent magnetic properties. The resulted short (310 nm in length) and wide (50 nm in diameter) Co nanowires present only hexagonal close-packed phase, with the coercivity and squareness ratio as high as 1.2 x 10(5) A/m and 0.803, respectively. The magnetization reversal mechanism is in good agreement with coherent rotation model. The color and magnetic properties remain the same over a wide temperature range. The Co-containing anodic aluminum oxide films with structural color and perpendicular magnetic recording properties have friability-resistant feature and could be used in many areas including decoration, display and multifunctional anti-counterfeiting applications.Dyes and Pigments 12/2014; 111:185–189. DOI:10.1016/j.dyepig.2014.06.012 · 3.47 Impact Factor
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ABSTRACT: Bi4Ti3O12 (BTO) doped with different concentrations of Er3+ was prepared using sol–gel method. Their structures and surface morphology were examined by X-ray diffraction, Raman spectroscopy and scanning electron microscopy, respectively. All XRD peaks can be indexed according to orthorhombic BTO phase, which is consistent with Raman measurement results. Strong upconversion green luminescence is observed in the Er3+ doped BTO powders pumped by 980 nm at room temperature. Three upconversion emission bands centered at about 525, 550 and 662 nm are due to the radiative relaxation of Er3+ from 2H11/2, 4S3/2 and 4F9/2 to the ground level 4I15/2, respectively. The upconversion emission mechanism of the samples were identified and analyzed. In addition, the doped BTO ceramics show obvious hysteresis loops, demonstrating the ferroelectric properties of the samples. These results illustrate the potential of this class of materials for photonic applications in optoelectronics devices.Journal of Sol-Gel Science and Technology 08/2011; 59(2). DOI:10.1007/s10971-011-2498-4 · 1.55 Impact Factor
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ABSTRACT: We report the structural and optical properties variation of Bi4-xNdxTi3O12 by different Nd substitution content for the first time. Bi4-xNdxTi3O12 thin films were fabricated by sol-gel process. X-ray diffraction and Raman scattering analysis reveal degradation in crystallinity and increase in distortion upon Nd doping. Grain size is suppressed as the increase of Nd content. Optical transmittance decreases from 63% to 43% at the wavelength of 600 nm as the Nd content increases from 0 to 0.85. Band gap energy increases from 3.4 to 3.5 eV when Nd content increases. Refractive index and extinction coefficient variations are also investigated.Integrated Ferroelectrics 01/2012; 133(1):73-80. DOI:10.1080/10584587.2012.670058 · 0.37 Impact Factor