Showing papers by "Shigeo Mori published in 2011"
TL;DR: In this paper, a characteristic nonlinear electric response was found in a charge ordered type ferroelectrics LuFe2O4 with less oxygen deficiency, which may relate to the electron hopping in the charge stripe structure.
Abstract: A characteristic nonlinear electric responses were found in a charge ordered type ferroelectrics LuFe2O4 with less oxygen deficiency. Cole – Cole circular in the dielectric response varies in the function of the amplitude of the AC electric field. With a synchrotron radiation diffraction experiment under the current revealed the variation of the coherence length of the polar charge ordered W-layer along c-axis. The nonlinear response with the increase of the electronic current may relates to the electron hopping in the charge stripe structure.
10 citations
6 citations
TL;DR: In this article, a morphotropic phase boundary between the rhombohedral and pseudo-cubic phases is present in 0.5K 0.4 < x < 0.43.
Abstract: Crystal structures and dielectric, polarization, and piezoelectric properties of x(Bi0.5K0.5)TiO3-(1–x)BiFeO3 ceramics were investigated. The results obtained using x-ray and neutron powder diffractions show that a morphotropic phase boundary between the rhombohedral (ferroelectric) and pseudo-cubic (ferroelectric) phases is present in 0.4 < x < 0.43. Ceramics with x = 0.4 exhibited a large remanent polarization of 52 μC/cm at 25 °C (1Hz). In addition, ceramics with x = 0.4 showed a relatively large electric-field-induced strain (Smax/Emax = 250 pm/V) at a high temperature of 200 °C. Transmission electron microscopy for x = 0.4 provides evidence of polar nanosized domains with R3c rhombohedral structure. It is suggested that the presence of the nanosized domains is the origin of relaxor-like dielectric behavior.
5 citations
TL;DR: In this paper, a series of Ti-Fe-C-N alloys were prepared and a constitutional diagram was constructed as a function of N and Fe contents for the formation of α-Ti precipitation.
Abstract: High strength with high ductility can be achieved in the titanium alloys by using metal precipitated ceramic particle as reinforcement. In this work, α + β or β-Ti alloy composites were prepared with α-Ti precipitated TiC particles. A series of Ti–Fe–C–N alloys were prepared and a constitutional diagram was constructed as a function of N and Fe contents. Two criteria were identified for the formation of α-Ti precipitation. One is the existence of Ti2C phase and the other is the presence of α-Ti phase in the matrix. The mechanism of α-Ti formation from the Ti2C phase is discussed.
4 citations
29 Oct 2011
TL;DR: In this article, the authors examined formation processes of ordered array of two types of rectangular nanorods, characterized as chessboard-type (CB-type) nanodomain structures, by changing the isothermal annealing time at 648 K.
Abstract: We examined formation processes of ordered array of two types of rectangular nanorods, characterized as chessboard-type (CB-type) nanodomain structures, by changing the isothermal annealing time at 648 K. Highly organized CB-type nanodomain structures developed through the isothermal annealing treatment from 10 to 730 hours and consequently the CB-type nanodomain structures with ~50 nm2 in size are formed in samples annealed for 730 hours. From the chemical composition analysis, it is revealed that the two types of rectangular nanorods comprise the coexisting state of one nanorod with composition close to CoFe1.4MnO4 with the cubic structure and another nanorod with composition close to CoFe0.4Mn2O4 with the orthorhombic structure.
3 citations
29 Oct 2011
TL;DR: In this paper, changes of charge ordered (CO) structure by partial substitution of Mn for Fe in YbFe2O4 were investigated by a transmission electron microscope (TEM) in combination with conventional dielectric measurement.
Abstract: Changes of charge ordered (CO) structure by partial substitution of Mn for Fe in YbFe2O4 were investigated by a transmission electron microscope (TEM), in combination with conventional dielectric measurement. It is revealed that partial substitution of Mn2+ for Fe2+ in YbFe2O4 destroyed drastically the CO structure with the wave vector of q = . Consequently polar clustering structure giving rise to honeycomb-shaped diffuse streaks was found in YbFeMnO4. The random distribution of polar clustering structure gives rise to characteristic broad dielectric dispersion.
2 citations
24 Jul 2011
TL;DR: In this article, the nanoscaled lamella-type domain structures with the ∼10 nm width inside the macroscopic-sized banded domains with the 100∼200 nm width are characterized.
Abstract: Nanometric domain configuration of (1−x)Pb(Mg 1/3 Nb 2/3 )O 3 -xPbTiO 3 ((1−x)PMN-xPT) single crystals in the monoclinic phase around a morphotropic phase boundary (MPB) has been examined thoroughly by means of a transmission electron microscopy (TEM). Domain structures with hierarchically inhomogeneous configuration were found in the monoclinic phase near the MPB region around x∼0.32, which are characterized as the nanoscaled lamella-type domain structures with the ∼10 nm width inside the macroscopic-sized banded domains with the 100∼200 nm width. To elucidate formation processes of the domain structures with hierarchically inhomogeneous configuration, an in-situ TEM observation of changes of the domain structures in the temperature window between 298 K and 500 K was carried out. It is revealed that these nanoscaled lamella-type domain structures with the ∼10 nm width appear inside the banded domains due to the tetragonal structure and are inherent to the monoclinic phase.
1 citations
TL;DR: In this paper, the authors investigated domain structures in Pb(Zr,Ti)O3 (PZT) ceramics whose composition lies on the morphotropic phase boundary (MPB) using transmission electron microscopy (TEM).
Abstract: We investigated domain structures in Pb(Zr,Ti)O3 (PZT) ceramics whose composition lies on the morphotropic phase boundary (MPB) using transmission electron microscopy (TEM) and evaluated the piezoelectric properties of PZT. We found that monoclinic nanosized domains (nanodomains), which form in tetragonal domains, strongly correlated with the piezoelectric properties of PZT. The degree of formation of nanodomains depends on the grain composition. Thus, controlling the homogeneity of grain composition in the ceramics is crucial for optimizing the piezoelectric properties of PZT.
1 citations
28 Sep 2011
TL;DR: In this article, the stability of charge ordered structure (CO) in charge and spin-frustrated ferrite YbFe2O4 was investigated by partial substitution of Mn2+ for Fe2+ in combination with conventional dielectric measurement.
Abstract: In order to clarify the stability of charge ordered structure (CO) in charge- and spin-frustrated ferrite YbFe2O4, we have investigated changes of the CO structure by partial substitution of Mn2+ for Fe2+ in YbFe2O4 by a transmission electron microscope (TEM), in combination with conventional dielectric measurement It is revealed that subtle substitution of Mn2+ for Fe2+ in YbFe2O4 destroyed drastically the CO structure with the wave vector of q = and, instead, induced polar clustering structure characterized by honeycomb-shaped diffuse scatterings in the reciprocal space The formation of polar clustering structure should be responsible for the characteristic dielectric dispersion