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

To study the structure of the core of an edge dislocation in ionic crystal, we measured the amplitude dependence of internal friction by automated Marx's composite oscillator method and the vibrational current caused by charged dislocations. The phase angle between vibrational current and strain suddenly changed by 180 degrees at a strain amplitude of 10-6. From this fact we discuss the structure of the dislocation core.

We developed Marx's 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.

Marx's composite oscillator method has been successfully automated for measuring internal friction and Young's modulus. The apparatus automatically finds the mechanical resonant frequency of the composite oscillator and keeps the strain amplitude constant, so that internal friction and the modulus can easily be measured and directly recorded on an X-t recorder. This device enables us to observe continuously the time dependence of the pinning and unpinning processes of dislocation by point defects. The error in strain amplitude is suppressed to within ±0.1%, while the internal friction value changes by 2 orders of magnitude. The operation of this system has been analyzed by automatic control theory, and the theoretical results are in good agreement with the experiment results. The analysis and the application of this method are presented here together with some experimental results.

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.