The REBa2Cu3O7-δ (RE= Y, Dy, Er) superconducting ceramics have been prepared via coprecipitation(COP) method from nearly saturated solutions of metal acetates and 2propanol solution of oxalic acid. The metal oxalates powders were subjected to thermal treatment of 12 hours calcination at 900oC. The pelletized powder was sintered for 15 hr at 920oC. All samples showed a single step transition in the R-T curves. The TC(R=0) for samples Dy123, Y123and Er123 and were 93 K, 91 K and 90 K, respectively. XRD data showed single phase of an orthorhombic structure for all samples. SEM micrographs showed large grain sizes that are randomly distributed. These results showed that COP method using metal oxalates starting powders is very effective to synthesize high quality superconductors and shorten the sintering time required due to the formation of sub micron oxalate powders.

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Polycrystalline samples with the nominal composition YBa2Cu3O7-δ (Y-123) were prepared using the co-precipitation method. The effect of the calcination process (single and multiple calcinations) on the samples was investigated by using the four-point temperature-resistance measurement, x-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM). This study is divided into two parts. For the first part, the obtained oxalate powder underwent two calcination processes at 900 °C for 12 h and 900 °C for 24 h, respectively. Then, the powders were pressed into pellets and sintered at 920 °C for 15 h with oxygen flow during the entire heat treatment. In the second part, only one calcination process was undertaken at 900 °C for 24 h before the sintering process in oxygen flow at 920 °C for 15 h. From the XRD patterns, all of the peaks were indexed to the Y-123 phase showing that this superconducting phase was already formed after the first calcination. The volume fraction of Y-123 of the samples with single calcination process was higher compared to multiple calcination processes. From the temperature-resistance measurement, all the samples showed metallic behavior in the normal state and a superconducting transition to zero resistance. The superconducting transition temperature, Tc, for the samples prepared in a single calcination process is higher than that of the multiple calcination processes.

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