YBa2Cu3O7?X 500–600 K Isostructural Phase Transition and Its Influence on Critical-Current Value

YBa₂Cu₃O_7–X ceramic samples voltage–current characteristics at 77 K and acoustic emission activity during thermocycling 500–600 K region have been studied. Partial oxygen sorption by these samples through heating has been established by critical-current value and acoustic emission activity at 540–550 K. During thermocycling an acoustic emission maximums have been observed on 3rd and 6th thermocycles, and these maximums correlate with some decrease of the critical-current value. It is shown that observed acoustic emission maximums are because of a phase-work hardening during thermocycling of these samples. A mechanism of this phase-work hardening influencing the critical-current value in YBa₂Cu₃O_7–X ceramic samples is discussed.