The Experts below are selected from a list of 29270106 Experts worldwide ranked by ideXlab platform
Satoshi Sasaki - One of the best experts on this subject based on the ideXlab platform.
-
Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases
Acta Crystallographica Section B Structural Science Crystal Engineering and Materials, 2016Co-Authors: Tomotaka Nakatani, Akira Yoshiasa, Akihiko Nakatsuka, Tatsuya Hiratoko, Tsutomu Mashimo, Maki Okube, Satoshi SasakiAbstract:A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298–778 K. A transition from a tetragonal (P4mm) to a cubic (Pm \overline 3 m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti4+ and Ba2+ cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.
-
Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases.
Acta crystallographica Section B Structural science crystal engineering and materials, 2016Co-Authors: Tomotaka Nakatani, Akira Yoshiasa, Akihiko Nakatsuka, Tatsuya Hiratoko, Tsutomu Mashimo, Maki Okube, Satoshi SasakiAbstract:A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.
Shunai Che - One of the best experts on this subject based on the ideXlab platform.
-
self assembly of α helices to form rare two dimensional square P4mm symmetry via silica mineralization
Chemistry: A European Journal, 2013Co-Authors: Yuan Yao, Lu Han, Dong Wang, Shunai CheAbstract:Space oddity: The synthesis of a polypeptide-silica complex with a rare two-dimensional square P4mm structure is reported. The electrostatic "zipping" of the interacting amino and carboxylate groups along the α-helices and the diagonal formation of the silica wall between the α-helices were optimal for the identical azimuthal orientation of α-helices toward 2D square P4mm structure, which generated a new polypeptide liquid crystal phase diagram.
-
Self‐Assembly of α‐Helices to Form Rare Two‐Dimensional Square P4mm Symmetry via Silica Mineralization
Chemistry (Weinheim an der Bergstrasse Germany), 2013Co-Authors: Yuan Yao, Lu Han, Dong Wang, Shunai CheAbstract:Space oddity: The synthesis of a polypeptide-silica complex with a rare two-dimensional square P4mm structure is reported. The electrostatic "zipping" of the interacting amino and carboxylate groups along the α-helices and the diagonal formation of the silica wall between the α-helices were optimal for the identical azimuthal orientation of α-helices toward 2D square P4mm structure, which generated a new polypeptide liquid crystal phase diagram.
-
DNA–Silica Mineralization: The Formation of Exceptional Two Dimensional-Square P4mm Symmetry by a Structural Transformation
Chemistry of Materials, 2012Co-Authors: Lu Han, Chenyu Jin, Ben Liu, Shunai CheAbstract:DNA–silica complex (DSC) mesocrystals have been synthesized by the self-assembly of DNA as template, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS) as costructure directing agent (CSDA), and tetraethyl orthosilicate (TEOS) as the silica source. A full-scale synthesis-field diagram of DSCs has been constructed, and fibrous products, two-dimensional (2D)-hexagonal p6mm, and 2D-square P4mm platelets have been obtained by varying the synthetic conditions. The rare 2D-square structure possessed an inconsistent hexagonal morphology and appeared as the dominant mesostructure. The combination of X-ray diffraction patterns, scanning electron microscopy images, and high-resolution transmission electron microscopy images provided visible evidence for the mesostructural constructions of the 2D-square symmetry that transformed from the 2D-hexagonal symmetry. The driving force for this transformation seems to be the polymerization of the silica species during synthesis, which caused a decrease in the ...
-
dna silica mineralization the formation of exceptional two dimensional square P4mm symmetry by a structural transformation
Chemistry of Materials, 2012Co-Authors: Lu Han, Chenyu Jin, Ben Liu, Shunai CheAbstract:DNA–silica complex (DSC) mesocrystals have been synthesized by the self-assembly of DNA as template, N-trimethoxysilylpropyl-N,N,N-trimethylammonium chloride (TMAPS) as costructure directing agent (CSDA), and tetraethyl orthosilicate (TEOS) as the silica source. A full-scale synthesis-field diagram of DSCs has been constructed, and fibrous products, two-dimensional (2D)-hexagonal p6mm, and 2D-square P4mm platelets have been obtained by varying the synthetic conditions. The rare 2D-square structure possessed an inconsistent hexagonal morphology and appeared as the dominant mesostructure. The combination of X-ray diffraction patterns, scanning electron microscopy images, and high-resolution transmission electron microscopy images provided visible evidence for the mesostructural constructions of the 2D-square symmetry that transformed from the 2D-hexagonal symmetry. The driving force for this transformation seems to be the polymerization of the silica species during synthesis, which caused a decrease in the ...
Tsutomu Mashimo - One of the best experts on this subject based on the ideXlab platform.
-
High-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type PbTiO3 phases.
Acta Crystallographica Section B Structural Science Crystal Engineering and Materials, 2016Co-Authors: Akira Yoshiasa, Tomotaka Nakatani, Akihiko Nakatsuka, Maki Okube, Kazumasa Sugiyama, Tsutomu MashimoAbstract:A high-temperature single-crystal X-ray diffraction study of a synthetic PbTiO3 perovskite was carried out over the wide temperature range 298-928 K. A transition from a tetragonal (P4mm) to a cubic (Pm \bar 3 m) phase has been revealed near 753 K. In the non-centrosymmetric P4mm symmetry group, the difference in relative displacement between Pb and O along the c-axis is much larger than that between Ti and O. The Pb and Ti cations contribute sufficiently to polarization being shifted in the opposite direction compared with the shift of O atoms. Deviation from the linear changes in Debye-Waller factors and bonding distances in the tetragonal phases can be interpreted as a precursor phenomenon before the phase transition. Disturbance of the temperature factor Ueq for O is observed in the vicinity of the transition point, while Ueq values for Pb and Ti are continuously changing with increasing temperature. The O site includes the clear configurational disorder in the cubic phase. The polar local positional distortions remain in the cubic phase and are regarded as the cause of the paraelectricity. Estimated values of the Debye temperature ΘD for Pb and Ti are 154 and 467 K in the tetragonal phase and decrease 22% in the high-temperature phase. Effective potentials for Pb and Ti change significantly and become soft after the phase transition.
-
Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases
Acta Crystallographica Section B Structural Science Crystal Engineering and Materials, 2016Co-Authors: Tomotaka Nakatani, Akira Yoshiasa, Akihiko Nakatsuka, Tatsuya Hiratoko, Tsutomu Mashimo, Maki Okube, Satoshi SasakiAbstract:A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298–778 K. A transition from a tetragonal (P4mm) to a cubic (Pm \overline 3 m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti4+ and Ba2+ cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.
-
Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases.
Acta crystallographica Section B Structural science crystal engineering and materials, 2016Co-Authors: Tomotaka Nakatani, Akira Yoshiasa, Akihiko Nakatsuka, Tatsuya Hiratoko, Tsutomu Mashimo, Maki Okube, Satoshi SasakiAbstract:A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.
Tomotaka Nakatani - One of the best experts on this subject based on the ideXlab platform.
-
High-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type PbTiO3 phases.
Acta Crystallographica Section B Structural Science Crystal Engineering and Materials, 2016Co-Authors: Akira Yoshiasa, Tomotaka Nakatani, Akihiko Nakatsuka, Maki Okube, Kazumasa Sugiyama, Tsutomu MashimoAbstract:A high-temperature single-crystal X-ray diffraction study of a synthetic PbTiO3 perovskite was carried out over the wide temperature range 298-928 K. A transition from a tetragonal (P4mm) to a cubic (Pm \bar 3 m) phase has been revealed near 753 K. In the non-centrosymmetric P4mm symmetry group, the difference in relative displacement between Pb and O along the c-axis is much larger than that between Ti and O. The Pb and Ti cations contribute sufficiently to polarization being shifted in the opposite direction compared with the shift of O atoms. Deviation from the linear changes in Debye-Waller factors and bonding distances in the tetragonal phases can be interpreted as a precursor phenomenon before the phase transition. Disturbance of the temperature factor Ueq for O is observed in the vicinity of the transition point, while Ueq values for Pb and Ti are continuously changing with increasing temperature. The O site includes the clear configurational disorder in the cubic phase. The polar local positional distortions remain in the cubic phase and are regarded as the cause of the paraelectricity. Estimated values of the Debye temperature ΘD for Pb and Ti are 154 and 467 K in the tetragonal phase and decrease 22% in the high-temperature phase. Effective potentials for Pb and Ti change significantly and become soft after the phase transition.
-
Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases
Acta Crystallographica Section B Structural Science Crystal Engineering and Materials, 2016Co-Authors: Tomotaka Nakatani, Akira Yoshiasa, Akihiko Nakatsuka, Tatsuya Hiratoko, Tsutomu Mashimo, Maki Okube, Satoshi SasakiAbstract:A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298–778 K. A transition from a tetragonal (P4mm) to a cubic (Pm \overline 3 m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti4+ and Ba2+ cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.
-
Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases.
Acta crystallographica Section B Structural science crystal engineering and materials, 2016Co-Authors: Tomotaka Nakatani, Akira Yoshiasa, Akihiko Nakatsuka, Tatsuya Hiratoko, Tsutomu Mashimo, Maki Okube, Satoshi SasakiAbstract:A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.
V. Yu. Topolov - One of the best experts on this subject based on the ideXlab platform.
-
Heterophase states and a bridging phase in (1‐x)BiScO3 − xPbTiO3
Crystal Research and Technology, 2012Co-Authors: V. Yu. TopolovAbstract:Heterophase ferroelectric solid solutions of (1-x)BiScO3 − xPbTiO3 are studied near the morphotrpic phase boundary (0.60 ≤ x ≤ 0.64). The role of non-180° domain types of the P4mm and R3m phases in heterophase structures is studied in the context of the phase content. It is shown that the bridging Cm phase coexists with the adjacent phase (either P4mm or R3m), and different variants of an elastic matching ‘single-domain Cm phase–polydomain P4mm phase’, ‘single-domain Cm phase–polydomain R3m phase’ and ‘single-domain Cm phase–near single-domain R3m phase’ promote the complete stress relief. Based on these concepts and considering a minimum number of the domain types in the coexisting phases, we find a molar-concentration dependence of the volume fraction of the Cm phase in the heterophase states. A correlation between the predicted volume fraction of the Cm phase and ratios of its unit-cell parameters is first revealed. The role of the intermediate R3m phase in the phase sequence R3c − R3m − Pmm and in the stress relief at x = 0.60 is discussed. Good agreement between the predicted and experimental data on the phase content is reached near the morphotrpic phase boundary.
-
Heterophase states and domain effects in solid solutions of (1 − x)BiFeO3 − xPbTiO3
Journal of Applied Physics, 2012Co-Authors: V. Yu. TopolovAbstract:Examples of heterophase states in multiferroic solid solutions of (1 − x)BiFeO3 − xPbTiO3 with the perovskite-type structure are studied taking into account the features of elastic matching of polydomain (twinned) ferroelectric phases near the morphotropic phase boundary and in a wide temperature range. Conditions for the complete stress relief are examined in the heterophase states P4mm–P4mm and P4mm–Cc to interpret variations of the phase content [S. Bhattacharjee et al., Phys. Rev. B 84, 104116 (2011)] [S. Bhattacharjee and D. Pandey, J. Appl. Phys. 110, 084105 (2011)] in (1−x)BiFeO3−xPbTiO3. The key role of some 90° domain types of the low-temperature ferroelectric P4mm phase in the stress relief at the phase coexistence is emphasized. An agreement between the evaluated and experimental data on the volume fraction of the low-temperature P4mm phase in heterophase samples is observed.
-
Correlation between non-180° domain structures in (1−x)PbA1∕3Nb2∕3O3−xPbTiO3 single crystals (A=Mg or Zn) under an applied [001] electric field
Journal of Applied Physics, 2007Co-Authors: V. Yu. Topolov, Dwight D ViehlandAbstract:This work is devoted to the study of heterophase states in (1−x)PbA1∕3Nb2∕3O3−xPbTiO3 or PAN−xPT (A=Mg or Zn) single crystals under an electric field ‖E‖[001]. The possibility of elastically matched phases in the transformational sequences of Pm3m→P4mm→Cm, Pm3m→Cm, and P4mm→Cm are considered with regards to non-180° domains and changes in lattice parameters. Systems of diagrams linking domain types with interfaces between coexisting polydomain phases in PMN–0.28PT and PZN–0.045PT crystals are given. An important role of an intermediate P4mm phase in achieving stress accommodation has been identified by analysis of lattice parameters of PMN–0.28PT, and the elastic compatibility conditions between non-180° domain structures in the P4mm and Cm phases have been determined for various heterophase states. Two scenarios of changes in the lattice parameter aT in the P4mm phase of PMN–0.28PT have first been discussed to reveal possibilities of stress accommodation in heterophase states. It has been shown that the ...
-
A new monoclinic phase and elastic effects in PbZr 1−x Ti x O 3 solid solutions
Physics of the Solid State, 2001Co-Authors: V. Yu. Topolov, A. V. TurikAbstract:The elastic matching of single-or polydomain ferroelectric phases R3m-P4mm, Cm-P4mm, and R3m-Cm and the relaxation of mechanical stresses in PbZr1−xTixO3 solid solutions are investigated. The conditions for constancy of the optimum volume concentrations of twin domains of the P4mm and Cm phases in the vicinity of the morphotropic phase boundary in the x-T diagram are analyzed, and the correlation between the morphotropic boundary and interfaces, namely, the planes of zero mean strains, is discussed.
-
Interphase boundaries and high piezoelectric activity of xPbTiO3-(1−x)Pb(Zn1/3Nb2/3)O3 crystals
Physics of the Solid State, 2001Co-Authors: V. Yu. Topolov, A. V. TurikAbstract:Model concepts of the interphase boundaries whose displacements are capable of substantially affecting the piezoelectric properties of xPbTiO3-(1−x)Pb(Zn1/3Nb2/3)O3 multidomain crystals in the R3m-P4mm morphotropic region are developed. The contributions of the interphase boundaries Δd33 to the piezoelectric modulus d33 are determined, and the factors responsible for the large ratios Δd33/d33≈0.5–0.9 are analyzed.
