YBa₂Cu₃O_7-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 phasework hardening influencing the critical-current value in YBa₂Cu₃O_7-x ceramic samples is discussed.