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Browsing by Author "Luo, Liang"

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    Observation of partially incoherent <110> boundaries between polar nanodomains in Na1/2Bi1/2TiO3 single crystals
    Yao, Jianjun; Ge, Wenwei; Yang, Yaodong; Luo, Liang; Li, Jiefang; Viehland, Dwight D.; Bhattacharyya, Somnath; Zhang, Qinhui; Luo, Haosu (American Institute of Physics, 2010-09-15)
    The ferroelectric domain structure of Na1/2Bi1/2TiO3 single crystals was investigated by transmission electron microscopy (TEM) and piezoforce microscopy (PFM). Bright-field TEM and PFM images revealed the presence of polar nanodomains, whose boundaries had a tendency to align along the < 110 >. High resolution TEM images revealed planar defects along these < 110 > boundaries, which partially relaxed the coherency of the lattice. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488879]
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    Raman spectroscopic study of Na1/2Bi1/2TiO3-x%BaTiO3 single crystals as a function of temperature and composition
    Luo, Liang; Ge, Wenwei; Li, Jiefang; Viehland, Dwight D.; Farley, Charles; Bodnar, Robert J.; Zhang, Qinhui; Luo, Haosu (American Institute of Physics, 2011-06-01)
    A Raman spectroscopic study of Na1/2Bi1/2TiO3-x%BaTiO3 (NBT-x%BT) single crystals with x=0 and 5.6 has been performed as a function of temperature from 25 to 600 degrees C. The general features of the Raman spectra for the various compositions were similar over the region of the phase diagram investigated, with only subtle changes between rhombohedral (R), tetragonal (T) and cubic phases. The peaks were broad, with no significant narrowing on cooling through a phase transition. We find evidence of an oxygen octahedral rotational mode in the paraelectric state. On cooling near and below the ferroelectric Curie temperature, a gradual change in intensity of the A-O and B-O peaks occurred with decreasing temperature. Evidence of a ferroelectric -> antiferroelectric transition was found near 200-250 degrees C, consistent with the onset of dispersion in the dielectric constant. The phase transition mechanism was discussed. The findings indicate the presence of a broad distribution of quasistatic local structural distortions, which only have subtle differences in the various average structures. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3587236]