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Abstract
A theory for the relationship between the mechanical damping, compliance defect, piezoelectric moduli and electric susceptibility due to charged dislocations is discussed. A damping and piezoelectric (direct and converse) experiment on a <100> single crystal of KCl at 40 kHz and strain amplitudes of 1·6 × 10−10 to 1·5 × 10−5 is reported. The method is shown to be suitable for the measurement of a piezoelectric modulus as small as 5 × 10−19 coulomb/newton. The mechanical damping, compliance defect and piezoelectric modulus are found to be strongly amplitude dependent above a strain of 3 × 10−7. From this experiment the charge on the dislocations is calculated to range between 1 and 3% of the maximum allowed on a dislocation. The behaviour of this measured charge with strain amplitude suggests that the damping is due to charged dislocations interacting with their compensating charge clouds. The charge cloud radius of 13 Å calculated from the impurity concentration agrees favourably with the value of 20 Å obtained from the experimental results suggesting that the restrictions on the theory for eV ∞/kT>l are not severe. The electric susceptibility due to charged dislocations is estimated as 10−4.