Tc, Hc, and oxygen ordering in quenched oxygen deficient YBa2Cu3O7-δ

The reversible magnetization as a function of field and temperature of polycrystalline Y Ba2Cu3O7-δ (0<δ<0.5) was measured. Specimens quenched from high temperatures (>550 degrees C) exhibit an almost linear decrease of Tc vs δ. The magnetization data is in excellent agreement with calculated values obtained from Ginzburg-Landau (GL) theory. However, large values (> 200) for the GL parameter κ are necessary to fit the data, leading to large values of the upper critical field slope. Both Hc(T = 0) and κ decrease with increasing oxygen deficiency. Selected area diffraction (SAD) patterns were obtained in a transmission electron microscope (TEM) on selected specimens. The SAD patterns obtained from high temperature quenched specimens are quite different from those obtained on slow-cooled specimens. A single parameter model was developed that uses microdomains made of Ortho I, Ortho II and Ortho III - like units to build a materials of specific δ and oxygen configuration. The model is able to fit the measured diffraction patterns found in both quenched and slow-cooled specimens