Optimization of the superconductor YBa2Cu3O7−δ: The effect of the edos, processing conditions, impurities and Fe doping on the specific heat, Meissner effect and susceptibility

✍ Scribed by Alain Junod

• Publisher: Elsevier Science
• Year: 1988
• Tongue: English
• Weight: 331 KB
• Volume: 153-155
• Category: Article
• ISSN: 0921-4534
• DOI: 10.1016/0921-4534(88)90203-1

✦ Synopsis

We present specific heat data (30-300K) for twelve YBa2Cu307_ 6 samples prepared by various techniques, in relation to density, Meissner effect, a.c. and d.c. susceptibility, X-ray and neutron diffraction data. The jump AC/T c is closely related to the temperature-independent component of the susceptibility, Xo. The best samples, prepared by chemical methods, are characterized by 6-0.09, 60% true Meissner effect in 17 Oe, Xo = 293~emu/mole-f.u., AC/T e = 57 mJ/(K2mole-f.u.), and do not show intrinsic peaks near 240K. T e does not depend on the DOS. Further data for a sample with 99% density, for a sample before and after oxygen depletion, and for Fe-doped samples showing non-bulk superconductivity in the tetragonal phase are reported. Low temperature specific heat data (I-20K) are presented for six samples of YBa2Cu307, and for the possible impurity phases YBa2Cu306, YBa3Cu207, Y2BaCuO5, CuO and BaCuO 2. All the superconducting samples have a non-zero, sample-dependent linear term ~* at low temperature. This anomalous behaviour is presumably not an intrinsic property of the superconducting phase, as evidenced by the correlation between ~* and the Curie component of the susceptibility.