Observation of acoustic emission in high-<i>T</i> <i>c</i> YBa2Cu3O7–<i>x</i> superconductor at 300, 77, and 4.2 K under loading
Abstract
Acoustic emission (AE) is studied in the process of loading the samples of high-Tc superconductor YBa2Cu3O7–x at temperatures 300, 77 and 4.2 K. In the region of room temperature, one or two AE spikes were observed under loading immediately preceding fracture (σ = 80 MPa). At 77 K, the first AE spikes were observed at (σ = 60–70 MPa in the form of large-amplitude pulses. Separate large-amplitude AE spikes were also recorded during unloading of the samples. The nature of AE at 4.2 K was qualitatively different. Continuous emission emerged at σ = 5–10 MPa and was supplemented with large-amplitude AE spikes starting from the values σ = 10–15 MPa. The Keiser effect was observed for continuous emission. An analysis of AE signals leads to the conclusion that the YBa2Cu3O7–x high-Tc superconductor must possess an appreciable plasticity at 77 and 4.2 K. It is expected that the contribution of irreversible plastic deformation increases as the temperature decreases from 77 to 4.2 K.