Showing papers by "Yoshihiro Ishibashi published in 1990"
TL;DR: By applying the Landau theory, the appearance of the antiferroelectric phase in smectic liquid crystals and the double hysteresis loop are interpreted Several types of phase sequences are obtained phenomenologically.
Abstract: By applying the Landau theory, the appearance of the antiferroelectric phase in smectic liquid crystals and the double hysteresis loop are interpreted Several types of phase sequences including the antiferroelectric, ferroelectric and/or ferrielectric phase are obtained phenomenologically The D-E curves in the antiferroelectric phase are classified into three types depending on temperature and the coefficients of the fourth-order terms in the free energy
116 citations
TL;DR: In this article, the early stage of the polarization reversal in the present model coincides with what described by the Kolmogorov-Avrami (KA) model, and the characteristics of the model are discussed in the relationship with the KA model.
Abstract: The ferroelectric switching process has been studied on the basis of a one-dimensional discrete lattice model. The characteristics of the model is discussed in the relationship with the Kolmogorov-Avrami(KA) model. It has turned out that the features in the early stage of the polarization reversal in the present model coincides with what described by the KA model.
72 citations
TL;DR: In this article, the authors studied the switching behavior of antiferroelectric liquid crystal displays and designed the fundamental waveforms for multiplex driving and constructed a prototype display which works at room temperature.
Abstract: Smectic layer structure and switching behavior in antiferroelectric liquid crystals TFMHPOBC, TFMHPDBC and MHPOBC were studied. At the phase transition point between SmC* and SmCA*, discontinuity in the leaning angle and the layer spacing was observed. In the SmA phase, diffraction peaks attributable to the focal conic texture and the planar layer structure were observed, implying that the bookshelf structure and the focal conic texture coexist. Using the tristable switching, we designed the fundamental waveforms for multiplex driving and constructed a prototype antiferroelectric liquid crystal display which works at room temperature.
71 citations
TL;DR: In this article, the effect of optical purity on the antiferroelectric phase transition and the field-induced ferromagnetic phase transition in Sm CA* was studied by means of dielectric measurements and observations of D-E hysteresis loops.
Abstract: The effect of optical purity on the antiferroelectric phase transition and the field-induced ferroelectric phase transition in Sm CA* were studied by means of dielectric measurements and observations of D-E hysteresis loops. The Curie-Weiss law was found to hold in Sm A and the Curie-Weiss constant to increase as the optical purity is reduced. Three types of D-E curves were obtained in the Sm CA* phase. It was found that a double hysteresis loop changed into a single one at high frequencies. The results obtained are discussed on the basis of a phenomenological theory.
42 citations
TL;DR: In this paper, the authors studied the layer structure of the antiferroelectric liquid crystal MHPOBC and observed a thermal hysteresis, i.e., a chevron structure was formed in the cooling process and a bookshelf structure in the heating process.
Abstract: The layer structure of the antiferroelectric liquid crystal MHPOBC was studied by X-ray measurements. We observed a thermal hysteresis in the layer structure; i.e., a chevron structure was formed in the cooling process, and a bookshelf structure in the heating process. It was found that the layer spacing decreases discontinuously at the Sm C*-Sm CA* transition point for an enantiomeric mixture in the cooling process. The result is discussed on the basis of a phenomenological theory.
39 citations
TL;DR: In this paper, the dielectric dispersion in the ferroelectric and antiferroelectric phases of a smectic liquid crystal, 4-(1-methylheptyl-oxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC), has been measured with several frequencies between 100 Hz and 100 kHz.
Abstract: The dielectric dispersion in the ferroelectric and antiferroelectric phases of a smectic liquid crystal, 4-(1-methylheptyl-oxycarbonyl)phenyl 4'-octyloxybiphenyl-4-carboxylate (MHPOBC), has been measured with several frequencies between 100 Hz and 100 kHz. The soft mode with the Debye-type dispersion was observed in the phase transition from the Sm A phase to the ferroelectric Sm C* phase. In the Sm C* phase, the Goldstone mode was observed at the frequency of about 4.5 kHz. The dielectric dispersion in the Sm CA*, Sm Cα* and Sm Cγ* phases is discussed.
39 citations
TL;DR: In this paper, the fundamental aspects of the structure, the energies of the formation and of the activation of domain walls are reviewed for several one-dimensional model systems and the effect of discreteness of atomic lattices on the structure and the activation energy of the domain walls is described.
Abstract: The fundamental aspects of the structure, the energies of the formation and of the activation of domain walls are reviewed for several one-dimensional model systems. The effect of discreteness of atomic lattices on the structure and the activation energy of domain walls is described. The motion of walls will be also mentioned.
36 citations
TL;DR: The temperature dependence of Raman spectra of lithium diborate (Li 2 B 4 O 7 ) was measured at temperature range from 300 K to 900 K as mentioned in this paper, implying that no displacive-type phase transition takes place there.
Abstract: The temperature dependence of Raman spectra of lithium diborate (Li 2 B 4 O 7 ) was measured at temperature range from 300 K to 900 K. At room temperature, 12 A 1 , 12 B 1 , 15 B 2 and 22 E modes were observed by various scattering geometries. No soft mode was observed in the above temperature range, implying that no displacive-type phase transition takes place there.
33 citations
TL;DR: In this article, the frequency and temperature dependences of dielectric properties of lithium diborate (Li 2 B 4 O 7 ) single crystal were investigated from 100 Hz to 100 kHz.
Abstract: The frequency and temperature dependences of dielectric properties of lithium diborate (Li 2 B 4 O 7 ) single crystal were investigated from 100 Hz to 100 kHz. Anomalous behavior of the real part of the dielectric constant e ′ was observed in the temperature range 300∼600 K. The anomaly observed in e ′ may be due to dielectric relaxation caused by the ionic conduction. The behavior of imaginary part of dielectric constant e ′′ can be well explained in terms of the ionic conduction.
33 citations
TL;DR: In this paper, the temperature dependences of dielectric dispersion in (CH 3 NH 3 ) 5 Bi 2 Cl 11 and CH 3 NH3 ) 5 B 2 Br 11 single crystals, which undergo the para-ferroelectric phase transition (I→II) at 307 K and 311.5 K respectively, were measured near the phase transition point in the frequency range from 1 MHz to 1 GHz.
Abstract: The temperature dependences of dielectric dispersion in (CH 3 NH 3 ) 5 Bi 2 Cl 11 and (CH 3 NH 3 ) 5 Bi 2 Br 11 single crystals, which undergo the para-ferroelectric phase transition (I→II) at 307 K and 311.5 K, respectively, were measured near the phase transition point in the frequency range from 1 MHz to 1 GHz. The dielectric dispersion exhibited was found to be of the Debye-type. The critical slowing down was observed near the phase transition point.
29 citations
TL;DR: In this paper, GaPO4 single crystals of the low-temperature form were hydrothermally grown in 4M H3PO4 solution at 180 ° C. The dielectric properties of grown crystals were measured with the electric field parallel (E ∥c) and perpendicular (E ⊥c), to thec-axis.
Abstract: GaPO4 single crystals of the low-temperature form were hydrothermally grown in 4M H3PO4 solution at 180 ° C. Single crystals 5.0×5.2×3.7mm3 in size could be grown in a silica glass vessel of 10 mm inner diameter. The dielectric properties of grown crystals were measured with the electric field parallel (E ∥c) and perpendicular (E ⊥c) to thec-axis. The values of dielectric constant (ie2800-01) ofE ∥c andE ⊥c are about 10.3 and 7.8, respectively, at frequencies from 10 kHz to 1 MHz, and these are nearly independent of frequency at room temperature. However, these values increase with temperature in the temperature range about 310 to 500 K and in the frequency region below 1 MHz. Dielectric loss (ie2800-02) increases with increasing temperature at around 300 K (E ∥c) and 310 K (E ⊥c). From the log σ (conductivity) against 1/T plot in the intrinsic region at higher temperatures, the values of activation energy (E) for conduction are calculated to be about 0.17 and 0.33eV, forE ∥c andE ⊥c, respectively.
TL;DR: In this article, the temperature-concentration phase diagram of a high-T c superconductor La 2-x Ba x CuO 4 system is reproduced satisfactorily with the use of a Landau-type thermodynamic potential, where a sixth-order term in the transition parameters is taken into account.
Abstract: The temperature-concentration phase diagram of a high- T c superconductor La 2- x Ba x CuO 4 system is reproduced satisfactorily with the use of a Landau-type thermodynamic potential, where a sixth-order term in the transition parameters is taken into account.
TL;DR: In this paper, the Raman spectra of α-GaPO 4 single crystals have been investigated at room temperature under atmospheric pressure, and the results are well in accordance with those obtained for the single crystals of the same structure such as quarts and AlPO 4.
Abstract: The Raman spectra of α-GaPO 4 single crystals have been investigated. In the polarization measurements at room temperature under atmospheric pressure we observed seven new Raman lines, not observed so far. In addition, the measurements of the temperature and pressure dependences of Raman spectra show the results which are well in accordance with those obtained for the single crystals of the same structure such as quarts and AlPO 4 .
Abstract: We observed ferroelastic domain of LaNbO 4 crystals by micro-Raman spectroscopy utilizing a specific band (107 cm -1 A g mode) with the polarization condition. We found the variation of the Raman intensity corresponding to the ferroelastic domain structure, which is caused by the rotation of crystallographic axes in each domain. The results were in accordance with the optical microscope image with a good reproducibility, proving the feasibility of micro-Raman spectroscopy in the study of domain structures.
TL;DR: In this paper, the low-temperature transition in K 2 Ba(NO 2 ) 4 is analyzed using a Landau-type thermodynamic potential function, and it is found that the lowtemperature phase must be monoclinic if the transition is induced by the instability of a mode at k 0 =(1/2, 1/2, 1/ 2, 1 2) of the Pbam phase.
Abstract: The low-temperature transition in K 2 Ba(NO 2 ) 4 is analyzed using a Landau-type thermodynamic potential function, and it is found that the low-temperature phase must be monoclinic if the transition is induced by the instability of a mode at k 0 =(1/2, 1/2, 1/2) of the Pbam phase.
TL;DR: In this paper, the temporal evolutions of the assembly of disclination lines, as well as of a single line, were studied from a fractal viewpoint. And the authors confirmed the validity of the relation µ=(D - D T )ν, where µ and ν are the exponents with respect to the disclination length and the characteristic length, respectively, and D and D T are the fractal and topological dimensions.
Abstract: The temporal evolutions of the assembly of disclination lines, as well as of a single line, are studied from the fractal viewpoint. It has turned out that the fractal dimension of the assembly is almost 2, while that of the single line is 1.65. We confirmed the validity of the relation µ=( D - D T )ν, where µ and ν are the exponents with respect to the disclination length and the characteristic length, respectively, and D and D T are the fractal and topological dimensions, respectively.
TL;DR: In this paper, the Tc -change in the mixed system of dicalcium strontium propionate was investigated on a two-sublattice model with special attention to the T c -change.
Abstract: Numerical calculation on a two-sublattice model was performed with special attention to the Tc -change in the mixed systems of dicalcium strontium propionate.
Journal Article•
TL;DR: In this paper, the effect of optical purity on the antiferroelectric phase transition and the field-induced ferromagnetic phase transition in Sm C A * was studied by means of dielectric measurements and observations of D-E hysteresis loops.
Abstract: The effect of optical purity on the antiferroelectric phase transition and the field-induced ferroelectric phase transition in Sm C A * were studied by means of dielectric measurements and observations of D-E hysteresis loops. The Curie-Weiss law was found to hold in Sm A and the Curie-Weiss constant to increase as the optical purity is reduced. Three types of D-E curves were obtained in the Sm C A * phase. It was found that a double hysteresis loop changed into a single one at high frequencies. The results obtained are discussed on the basis of a phenomenological theory
01 Jan 1990
TL;DR: In this article, the dynamics of interfaces in non-orthogonally twisted nematic liquid crystals were studied using a dynamical scaling law, and it was found that the scaling law holds well for the dynamics in the orthogonal twisted and non-nor-ortho-thick nematic cells.
Abstract: Dynamics of interfaces was experimentally studied, using nematic liquid crystals. It was found that the dynamical scaling law holds well for the dynamics in the orthogonally twisted nematic cell, while in the non-orthogonally twisted nematic cells the statistical equivalence could be found for the patterns formed in the cells with different twist angles. The evolution of patterns observed in the non-orthogonally twisted nematic cells is analyzed with the use of the theory which takes into account the effect of the initial distribution of interfaces.