Mitsuyoshi Matsushita

Giant electromechanical coupling factor of k31 mode and piezoelectric d31 constant in Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 piezoelectric single crystal

High-quality and large piezoelectric single crystals of Pb[(Zn1/3Nb2/3)0.91Ti0.09]O3 (PZNT91/09) fabricated by the Bridgman method were investigated regarding the material constants and their temperature dependence. The single crystals poled along [001] of the original cubic direction possess high piezoelectric constants such as g33 and g31 as well as high dielectric constant e33T/e0 (4600), electromechanical coupling factor of the k33 mode (95.3%) and d33 (2500 pC/N). In particular, since k31 and d31 reach 80.8% and -1700 pC/N, respectively, the crystals can be applied for use in sensors and actuators with high performance. Based on the temperature dependence, we inferred that there is a relatively large difference in the elastic compliance (s11E) between rhombohedral and tetragonal phases. The cause of the high piezoelectricity in rhombohedral PZNT91/09 single crystals is thought to be the mechanical softness which leads to easy deformation by the poling field in comparison with the tetragonal phase.

On the coherent electronic excitation of channelled He+ ions

Abstract Emission of light from He + ions transmitted though [111] axis of thin single crystal of gold has been studied and no effect of coherent electronic excitation could be detected.

Giant Piezoelectricity on k31 Mode in Pb(Mg1/3Nb2/3)O3-PbTiO3 Single Crystals

The giant k31 and piezoelectric d31 constant in Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMNT) single-crystal plates with dimensions of 13L?4.0W?0.34T/0.47T mm were investigated via the poling field dependence of the ferroelectric properties and by impedance response analysis on the k31 mode. Giant k31 over 86% was realized for (110) PMNT single-crystal plates under the conditions of a poling temperature of 40?C (pseudo-cubic phase), DC poling fields over 200 V/mm, and a poling time of 10 min. P?E hysteresis loops in (110) PMNT plates with giant k31 became asymmetric when the bipolar triangle pulse field exceeded 800 V/mm, which corresponds to the coercive field to obtain giant k31. The frequency response of impedance in (110) PMNT plates with giant k31 consisted of a single vibration in the length direction. Furthermore, since there were two frequency constants, 680 Hz-m on k31 (length direction) mode and 1425 Hz-m on k32 (width direction) mode, a single domain structure in the (110) PMNT single-crystal plate was confirmed by an anisotropy of their frequency constants. A mechanism to realize giant k31 can be explained by the relationship between the crystal plane and poling direction. The existence of a giant d31 constant was proven by the strain measurement as well as by the impedance measurement.

Effects of Dislocation on Planar Channelling of Energetic H+ and He+ Ions

Planar channelling of MeV H + and He + ions was studied using phosphorus implanted silicon crystals with a well-defined network of edge dislocations. The energy dependence of dechannelling at dislocation is shown to be proportional to the square root of the energy of the ion. The dechannelling processes of energetic charged particles at extended dislocation are discussed.

Direct scattering of channelling He ions at dislocations

Abstract The effects of misfit dislocations in epitaxial PbS/PbSe bi-crystals on the channeling of energetic He ions were studied. The direct scattering of channelling ions at dislocations was detected and its dependence on the energy of the incident ions was measured.

Dechannelling of Energetic Charged Particles at Dislocations in An-Ag Solid Solution

Dechannelling cross-section for MeV He ions of dissociated dislocation in Au-35 at % Ag alloy crystal is found to be several times as large as that of undissociated dislocation, which is estimated from the theoretical calculation by Quere. The dependence of the dechannelling cross-section of the dissociated dislocation on the energy E of the incident ions is proportional to E1/4, which is also different from that of undissociated dislocation.

Study of Slow Lattice Dynamics in Relaxor Ferroelectric PMN–30%PT by Neutron Spin Echo Technique

We have used the neutron spin echo technique to characterize the dynamics of polar nanoregions (PNRs) in the relaxor ferroelectric (1- x )Pb(Mg 1/3 Nb 2/3 )O 3 – x PbTiO 3 (PMN– x PT) with x =30% ( T C ∼400 K). We measured the normalized intermediate scattering function I ( Q , t )/ I ( Q ,0) for a butterfly-shaped diffuse scattering around the (100) Bragg point, which is associated with atomic shifts, i.e., polarizations in PNRs. For T ≥500 K, I ( Q , t )/ I ( Q ,0) shows a peak structure at 0.5 ns, which is ascribed to the coexistence of echo signals from a relaxation mode and those from a low-frequency vibrational mode with ω∼26 µeV. Such a low-frequency vibrational mode for directions indicate a flat free-energy surface between the rhombohedral and tetragonal phases. On cooling below 450 K, the peak structure in I ( Q , t )/ I ( Q ,0) disappears and diffuse scattering intensity increases, which indicates that the condensed or pinned low-frequency mode for directions is the origin of PNRs.

Observation of Lattice Defects in Single Crystals of Diacetylene (PTS) by X-Ray Topography

The defects in single crystals of diacetylene (PTS) are studied by X-ray topography (Langs method). Three types of isolated dislocations are observed and two kinds of Burgers vectors are determined. The first is the dislocation with the Burgers vector [001] and the slip plane (100), which has the straight part, which is the pure edge part. The second is the dislocation with the Burgers vector [211]. The third is the dislocation which is perpendicular to (100). In addition, the bundle of pure screw dislocations with the Burgers vector [010] and the planar defect are observed.

X-ray Intensity Fluctuation Spectroscopy Using Nanofocused Hard X-rays: Its Application to Study of Relaxor Ferroelectrics

The use of a combination of coherent X-rays from a third-generation synchrotron light source and ultraprecise Kirkpatrick-Baez mirrors enables us to apply nanofocused hard X-rays in solid-state physics. We developed an apparatus for X-ray intensity fluctuation spectroscopy using the nanofocused hard X-rays and applied it to the study of relaxor ferroelectrics. We have successfully detected a large and slow intensity fluctuation of scattered X-rays above cubic-to-tetragonal phase transition temperature with a characteristic time scale on the order of 10 s. We speculated that the intensity fluctuation originates from domain number fluctuation, which is directly related to the dielectric response, particularly the frequency dispersion.

Dechannelling of Fast Ions by Spherical G.P. Zones in Al-Zn and Al-Ag Alloy Single Crystals

Dechannelling of 1.5 MeV He + ions in planar channels of Al–6.8 at.% Zn and Al–8.2 at.%Ag alloy single crystals containing spherical G.P. zones was studied. Dechannelling cross sections of G.P. zones were obtained experimentaly from the normalized yields using single scattering model of dechannelling, and also calculated from the semi-analytical method based on the modified continuum model, taking account of both the lattice distortion around the zone and the sudden change of the planar potential at the zone. Lattice distortion around the G.P. zone was determined by comparison of the experimental and calculated dechannelling cross sections.