Highly crystalline single phase “2122”, Bi2CaSr2Cu2O8+δ, sample with δ=0.25 has been prepared from citrate precursors with pyrolysis. Stable and bulk superconductivity with T c(onset)=99 K and T c(zero)=95 K was reproducibly detected by the magnetic susceptibility and electrical resistivity measurements, respectively.

The reaction of superconducting YBa 2 Cu 3 Oy powder with water is studied kinetically. The initial rate law is found aso is the initial surface area of the solid, a and b is found to be 0.94 ± 0.02 and 0.318 ± 0.002, respectively. For 100.7 mg powder with a mean radius of 0.0265 mm at pH 7.00 and 298 K, Ro is 2.21 × 10 −4 mol · min −1 . Using a = 1 and b = 0.3, the rate constant, k, obtained at 283, 298 and 313 K is 0.64, 1.84 and 4.91 × 10 −3 mol · min −1 · cm −2 · M −0.3 , respectively. The activation energy is 50.0 kJ · mol −1 and pre-exponential factor is 1.09 × 10 6 mol · min −1 · cm −2 · M −0.3 , as calculated from the Arrhenius equation.

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Peritectic transition of a Bi-2223 superconductor was studied with TG and DTA under different heating rate (R, ~ and oxygen partial pressures. Linear relationships were observed between Tp (peritectic transition temperature) vs. R, and weight loss (equivalent to the O-atom loss per mole) vs. R under 25 mL/min in flowing 1% 02 partial pressure. Extrapolated to infinite rate, 0 ~ Tp was 821 ~ found from the peak temperature of the DTA curves, and 1.49 O-atom loss. Increasing oxygen partial pressure, Tp was increased but the weight loss was decreased. About 60 ~ difference in Tp was found between 1 and 100 % of partial oxygen pressure under 10~ heating rate. Only 0.26 O-atom loss was observed under 100 % oxygen partial pressure. Stability of Bi-2223 superconductor around its peritectic point was greatly enhanced by increasing the oxygen partial pressure.

A series of samples with a nominal composition of R3CaBa3Cu7Oy (abbreviated as R3137), where R = Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er and Tm, was prepared by a similar process as for an 80-K superconductor, La3CaBa3Cu7Oy. Most of the R3137 (except for R = Ce, Tb) had a tetragonal triple-perovskite phase like La3137 identified from the XRD patterns, and they were superconducting except Pr3137. For R3+ radius larger than Dy3+ (0.908 Å), a single phase R3137 was observed, and their Tc(zero)' probably related to the rCu-o distance in the copper-oxygen layer, was spread from 85 to 76 K with a maximum for the Eu3137. Oxygen stoichiometry of these R3137 was slightly decreased with decreasing lanthanide radii. The hole concentration, (Cu-O), was found between 0.47 and 0.38/unit cell. For Smaller R3+ ions, residual resistivity was found in the superconducting samples due to the existence of second phase. From the structural study of La3137, it was known that part of the lanthanide ions had to be fitted into the bigger Ba-site. Because ionic radii of the heavy lanthanides (R3+ < Ho3+ = 0.894 Å) were too small to be located at the Ba-site, it was rather difficult to prepare these single phase R3137.