Phase diagram of the Ba2YCu3O6-Ba2YCu3O7 system below 400°C

Mechanisms of interaction of YBa2Cu3O y with water vapor at low-temperature annealing

“…This indicates the rise of a rhombic distortion, probably connected with occupying oxygen vacancies by hydroxyl ions. In contrast to the treatment of samples of this composition at T = 200°C [5], the lines 200 and 006 do not expand and do not come closer, which indicates the absence of the 123 and pseudo-124 phase transitions.…”

“…Thus, the X-ray diffraction analysis has shown that, in contrast to annealing at T = 200-300°C [5], after the treatment at T = 100°C, samples of YBa 2 Cu 3 O y with different oxygen contents behave differently. At a low oxygen content, when there are many oxygen vacancies, the main process is the incorporation of hydroxyl groups into oxygen vacancies and, at y ≥ 6.5, the splitting of Cu-O chain with the transition of the 123 phase to the 124 pseudo-phase takes place.…”

“…The oxygen concentration was provided by thermal treatment at T = 900, 700, 500, and 400°C, respectively. The low-temperature treatment was performed at T = 100 and 150°C in an atmosphere saturated with water vapor [5] for 25-400 h. The water content was determined by gravimetry. The mass was measured with an error of ±0.005% (hereinafter, we use mass percents).…”

“…Moreover, at t ≤ 350°C, in the presence of atmospheric moisture, this compound decomposes into phases with different oxygen contents [4][5][6]. Due to splitting of Cu-O chains, the presence of water in the structure of YBa 2 Cu 3 O y leads to the formation of stacking faults with a thickness of 1.2-2.4 nm [1][2][3].…”

Effect of low-temperature treatment and subsequent high-temperature annealing on the critical current density of YBa2Cu3O y

“…The desired content of oxygen in the samples (y ≈ 6.8, 6.5, and 6.3) was attained by appropriate thermal treat ment at T = 500, 700 and 900°C, respectively, for 24 h [6]. The low temperature treatment was conducted at T = 200°C for 100 h in an argon atmosphere contain ing different amounts of moisture: a dry atmosphere (in the presence of silica gel annealed at T = 500°C), with a relative humidity of ~10% (argon passed through a saturated ZnCl 2 water solution), as well as in an atmosphere saturated with water vapor.…”