The electromagnetic emission (EME) from deformed ionic single crystals occurs due to the motion of charged dislocations. Observations of the EME from polycrystalline ductile materials have never been reported. Meanwhile, the boundaries between crystallites play the role of the natural barriers for sliding dislocations; therefore, one can expect that the character and degree of heterogeneity might affect substantially the manifestation of the EME excitation. This study presents results of the observation of the EME excited by the impact loading of ductile ionic‐covalent A2B6 ceramics. Continuous emission in the range of 10–100 kHz manifests itself in ZnS, ZnSe, and ZnTe compounds. This low‐frequency EME is supplemented with sporadic peaks emitted in the megahertz range. The continuous EME is ascribed by the motion of dislocations in crystallites, while the discrete high‐frequency emission is suggested to be due to discharges between edges of cracks nucleated at the final stage of the damage formation. The intercomparison of the EME time sweeps with the records of the mechanoluminescence and acoustic emission detected in parallel with the EME shows that the primary plastic deformation in the polycrystalline A2B6 compounds is followed by the accumulation of microcracks.
Nanocrystalline powders of magnesium aluminate spinel (MgAl 2 O 4 ) have been produced, and their morphological and structural properties have been studied. A comparative analysis of spinel samples synthesized by different liquid-phase methods has been carried out. Hot uniaxial pressing has been used to fabricate ceramic samples of spinel 15 mm in diameter and up to 2 mm thick.
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