Grain Boundary Flux Pinning Mechanism of Liquid-Phase-Sintered Bulk YBa2Cu3Ox

The peak effect in critical current density observed in liquid phase sintered YBa2Cu3Ox materials was investigated. The peak effect was observed in samples with a 900 °C precursor sintered at temperatures higher than 940 °C. However, samples with 950 °C precursor did not show the peak effect. Structural observation revealed that the appearance of the peak effect is closely related to grain growth but not directly with grain size. The observed oxygen annealing dependence indicated a discrepancy between the oxygen contents estimated using the obtained phase diagram and peak field, showing that a non-oxygen deficiency mechanism induces the peak effect. The behavior of a sample with a mixture of 900 and 950 °C precursors was consistent with the existence of oxygen deficiency and non-oxygen deficiency mechanisms. The high-oxygen-pressure annealing of a sample with Ag suggested that the peak effect observed in liquid-phase-sintering originates from the effect of magnetic flux pinning at grain boundaries.