Hiroto Tateno

Photoplastic Effect of NaCl Single Crystal

To clarify photoplastic effects, the Youngs modulus and internal friction of NaCl single crystals were measured by the automated Marxs composite oscillator method. The experimental results suggest that pinning of the metallic impurity and cation vacancy couples were released by light illumination, and the F-center and M-center produced by γ-ray irradiation emit internal free electrons.

Application to Vacuum Gauge of Marx's Composite Oscillator Method

By automated Marxs composite oscillator method, changes of internal friction with the pressure of nitrogen, oxygen, and argon were measured. The range of the measurement was from a pressure of 103 mbar to 10-5 mbar. An application to a wide range vacuum gauge was discussed.

Overtone-Drive in Marx's Composite Oscillator Method

We developed Marxs composite oscillator method to an automatic control system to keep the strain amplitude constant at fundamental and third overtone frequency. Stability of this control system is analyzed by an automatic control theory in the measurement of internal friction with varying strain amplitude, temperature, and external field. It is applied to measurement of a relaxation peak at a fundamental frequency of 50 kHz and overtone 150 kHz of the same specimen to study the relaxation process of AgCl.

Image of Ion Beam Excited Acoustic Microscope of the Teeth

The ion beam excited acoustic microscope (IAM) is a new microscope which provides visual representations of the elastic waves caused by localized chopping ion energy. Topographs and images of ultrasonic attenuation and local elastic variation were obtained by measuring frequency and amplitude at a composite resonant point between transducer and sample. Acoustic images of the teeth were measured by IAM. The elasticity of the hydroxyapatite crystal of the teeth was examined.

Ion Beam Excited Acoustic Image and Specific Element Image of Teeth

The ion beam excited acoustic microscope (IAM) is a new microscope which provides visual representations of the elastic waves caused by localized chopping ion energy. Topographs of ultrasonic attenuation and local elastic variations were obtained by measuring frequency and amplitude at a composite resonant point between transducer and sample. Specific ion images were also obtained from the same measurement. In this paper, the IAM and observed topographs and intensity modulated images of the specific ions are described. The elasticity of the hydroxyapatite crystal of the teeth is examined.

Dislocation string model and sweep-up vacancy

To verify the Granato–Lucke (G–L) theory, the internal friction and dislocation core current of NaCl single crystals are measured. Vacancies that move in-phase with dislocation cores and vacancies that undergo phase delay by dislocations are observed. Dislocations sweep up vacancies on the slip plane with the break-away strain amplitude. The accuracy of the G–L theory is demonstrated by subtracting the increase in friction due to sweep-up vacancies from the measured values. Corrections could also be performed for samples in which the number of vacancies had been changed by irradiation with gamma rays. The dislocation core of an irradiated sample is found to be negatively charged by an excess of vacancies in the small strain amplitude region.

Measurement of Diffusion of InCl3 in AgCl Single Crystal by Internal Friction

To study the behavior of divacancy and impurity, the diffusion process of InCl3 doped on the surface of a AgCl single crystal was measured by the internal friction and dielectric loss. All of the In3+ ions move to the dislocation core with a rate proportional to t1/6 and the migration energy is 0.060 eV. The concentration in the dipole of In3+ ion and cation vacancy rapidly becomes zero at the critical temperature 566 K. Reorientation of the dipole and ionic conductivity gives an identical migration energy of 0.33 eV. The binding energy between the vacancy and the trivalent impurity Eb is 0.10 eV.

Behavior of Hydrogen at Charged Dislocation in NaCl.

To study the structure of an edge dislocation core in an ionic crystal, we measured the amplitude dependence of internal friction by the automated Marxs composite oscillator method and the vibrational current caused by charged dislocations in a hydrogen-absorbed NaCl single crystal. The change of the sign of dislocation charge at the strain amplitude of 10-6 disappeared with absorption of hydrogen, while it was preserved using helium. These findings suggest that hydrogen exists as a positive ion in the dislocation core.

Analysis of Internal Friction Peaks in the Intermediate Temperature Range of NaCl

We measured internal friction, Youngs modulus, ionic conductivity corresponding to the density of vacancies and the dielectric loss corresponding to the dipole density at the same time by an automated Marxs composite oscillator method, in order to investigate the internal friction peaks of NaCl single crystal around 90°C. We observed peaks for both internal friction and dielectric loss, and interpreted the peaks to reflect relaxation by dipole reorientation.

Behavior of Dislocation Core in AgCl Single Crystal

To study the behavior of dislocation core in AgCl, we measured the amplitude dependence of internal friction by automated Marxs composite oscillator method and the vibrational current caused by charged dislocations, which are driven with the frequency of external force, fR=50 kHz. We obtained the association energy between vacancy and metallic impurity as EA=0.96 eV and the binding energy between dislocation and vacancy as Eb=0.66 eV combining ionic conductivity measurements.