ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
Superconducting 326 samples, La2−xSrxCaCu2Oz with x=0.2 and 0.4, which exhibited superconducting onsets at temperatures (Tonc's) higher than 40 K were successfully synthesized using hot-isostatic-pressing (HIP) techniques. As starting materials, powders of conventional carbonates (SrCO3 and CaCO3) and oxides (La2O3 and CuO) were employed. Sintering of the samples was made at a variety of temperatures (Ts) for 72 h in flowing O2 gas (of 1 atm). The sintered samples were post-annealed at various temperatures (Ta) for 6 h in a mixture of 80% Ar gas and 20% O2 gas of the total pressure of 1000 atm by means of HIP techniques. Optimum combinations of Ts and Ta were determined for obtaining superconducting samples. Single-phase samples were obtained only for the composition La1.8Sr0.2CaCu2Oz for which the oxygen content, z, was determined to be 6.01±0.01 by coulometric titration. It was concluded that Ta was a crucially important factor for obtaining superconducting 326 phase with Tonc (approximately-greater-than) 40 K, that is, Ta (approximately-greater-than) 970 °C was required (for 6-h HIP annealing). It was demonstrated that a long HIP annealing was necessary to obtain a significant volume fraction for the superconducting 326 phase.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.348560
