Modulus study of microcracks in single domain YBa2Cu3Ox with c-axis pressure during oxygen anneal

As the modulus is a quantitative measure of the bulk mechanical properties, it can serve as a sensitive probe for the crack propagation kinetics inside the materials. The YBa2Cu3Ox (YBCO) single domain with a tetragonal phase was pressed under a uniaxial pressure along the c-axis. The pressed sample was oxygenated at 400 °C for various time intervals up to 188 h. For each oxygenation interval, Young’s modulus was measured to study the effects of c-axis pressure on ab-plane crack propagation in single domain YBCO. The measurement was repeated along two directions: ab-plane (S) and c-axis (T), on the same sample annealed in flowing oxygen for various times. The experimental results showed that the modulus values of both directions remained unchanged for the entire oxygenation period, indicating that the ab-plane crack propagation was effectively suppressed. In contrast, it was found that, without the c-axis pressure, the modulus experienced a rapid fall when the sample had undergone a massive tetragonal-to-orthorhombic (T-to-O) transition.