Shock-Induced Electrical Polarization

It is of interest to compare the observations with different physical mechanisms as shown in Fig. 5.19. Typically, the polarization values for polymers are weak and do not overlap those of piezoelectrics. What is observed is that there is over a 6 order-of-magnitude range in polarizations from the weakest signals (Teflon) to the strongest (PZT 95-5). The polarization signals from ionic crystals are stronger than those in polymers and overlap those of piezoelectrics, albeit at larger strains. 

130 Chapter 5. Physical Properties Under Elastic-Plastic Compression 

Numerous observations of the effect in ionic crystals were carried out by Mineev and Ivanov in the Soviet Union [76M01]. This is a class of crystals in which a number of materials factors can be confidently varied. By choice of crystallographic orientation, various slip directions can be invoked. By choice of various crystals other physical factors such as dielectric constant, ionic radius, and an electronic factor thought to be representative of dielec- 

Several overall features of the shock-induced polarization are apparent. First, there appears to be a threshold compression below which the signals are not observed. The compression for this threshold is considerable, about 15%, such that it is not difficult to believe that the material must be considerably altered in structure before polarizations appear (shown in Fig. 5.22). Following the threshold compression, the polarizations increase extraordinarily rapidly with increasing compression, finally reaching a saturation value at compressions of perhaps 30%. 

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Shock-induced electrical polarization Mineev and Ivanov [76M01] (19, 148)... 

In this chapter piezoelectric crystals and polymers ferroelectric and ferromagnetic solids resistance of metals shock-induced electrical polarization electrochemistry elastic-plastic physical properties. 

Fig. 4.6. Piezoelectric pulse diagrams can be used to obtain explicit representations of the time dependent electric fields in piezoelectric substances. The magnitudes and orientations of these electric fields are critical to development of shock-induced conduction. As an example, the diagram on the left shows the polarization and displacement relations for a location at the input electrode. The same functions for a location within the crystal is shown on the right (after Davison and Graham [79D01]).

Finally, the phenomenon of shock-induced polarization represents perhaps the most distinctive phenomenon exhibited by shock-compressed matter. The phenomenon has no counterpart under other environments. The delineation of the details of the phenomenon provides an unusual insight into shock-deformation processes in shock-loading fronts. Description of the phenomenon appears to require overt attention to a catastrophic description of shock-compressed matter. In the author s opinion, a study of shock-induced polarization represents perhaps the most intriguing phenomenon observed in the field. In polymers, the author has characterized the effect as an electrical-to-chemical investigation [82G02]. 

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