Effect of Y/sub 2/BaCuO/sub 5/ and PtO/sub 2//spl middot/H/sub 2/O additions on the microstructural development in YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// superconductors

Results are presented concerning the formation kinetics of Y/sub 2/BaCuO/sub 5/ (211) and YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (123) phases during melt processing of melt quench (MQ) precursors and phase pure 123. The influence of Pt and 211 additions on microstructural development within YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// system are examined quantitatively via XRD analysis and DTA. Real time dynamic XRD analysis showed the phase reaction sequences for the MQ and phase pure 123 (SSC) precursor systems, and revealed the activation energy (E/sub a/) for 211 formation to be lower for MQ powders upon peritectic decomposition. The SSC precursors developed greater amounts of 211 at 1100/spl deg/C when compared to MQ precursors, (/spl sim/28 wgt% vs. 10 wgt% respectively). The addition of 0.5 m/o 211 additions in SSC resulted in lower 123 temperatures and E/sub a/ than that without 211 addition. Pt additions did alter the residual 211 content upon texturing. The presence of Pt with excess 211 additions was seen to inhibit 211 formation upon texturing.<
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