Electromagnetic Emission from Impact‐Loaded Polycrystalline A₂B₆ Materials

Abstract

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.

Impact and indenting damage of CVD-produced ZnS and ZnSe ceramics

“…The microcracking process in A 2 B 6 semiconductors is accompanied with the light emission (fractoluminescence) caused by the strain-stimulated motion of charged dislocations [15,16]. When reaching the ultimate strain, a fault with growing cracks emerges, which manifest themselves by sound generation [17]. The penetration speed of an indenter into ceramics was about three order of magnitude lower than that of a striker used in our impact experiments.…”

Ударное и "задержанное" повреждение поверхности керамики ZnS-CVD

“…Известно [6][7][8], что в пластичных кристаллах (включая ZnS [9]) первичная деформация при разрушении начинается с движения заряженных дислокаций. При достижении предельной деформации зарождаются микротрещины, проявляющиеся в генерации акустической эмиссии (АЭ) [9]. Движение дислокаций, приводящее к развитию разрушения, зависит от скорости подачи нагрузки.…”