Status of BSSCO powders work at Nexans SuperConductors Mark Rikel Jürgen Ehrenberg, Achim Hobl, Joachim Bock.

Presentation on theme: "Status of BSSCO powders work at Nexans SuperConductors Mark Rikel Jürgen Ehrenberg, Achim Hobl, Joachim Bock."— Presentation transcript:

1 Status of BSSCO powders work at Nexans SuperConductors Mark Rikel Jürgen Ehrenberg, Achim Hobl, Joachim Bock

2 Sept 2002 / 2 May 16, 2013 2 Acknowledgements Christian Sheuerelein (CERN); Mario Scheel, Marco Di Michiel (ESRF) Dirk Ewald (Clariant), Manfred Zimmer (InfraServ Knapsack) Rene Deul, Lisa Koliotassis, Alexis Camus, Simon Krämer, Andreas Klimt, Zemfira Abdoulaeva, Werner Horst (NSC)

3 Sept 2002 / 3 May 16, 2013 3 Goal Deliver precursor to OST for Wire Production restarting production of precursor optimizing particle size window for granular precursor material redo compositional experiments of 2004-2005 (precursor of various compositions). optimizing O contents in Bi2212 wires made using precursor materials of different composition. June 28, 2012

4 Sept 2002 / 4 May 16, 2013 4 First Tasks

5 Sept 2002 / 5 May 16, 2013 5 Restarting Production Precursor Produce 10 kg High-Quality Precursor Reestablish/Validate Technology and Quality-Control Procedures Technological steps  Double Check Mixing, Milling, and Sieving Equipment  Calibration of Furnaces (establish correspondence with DTA/TGA data)  Use proper compacting equipment Characterization Tools  Double Check XFA(EDX) for overall cation composition, IR spectroscopy (C), and ICP (impurities)  Calibration of DTA/TGA  Laser Granulometry versus SEM (what to trust?)  Rietveld Analysis of XRD patterns (understand reliability)

6 Sept 2002 / 6 May 16, 2013 6 New Lots 81, 82 ~50 kg lot 82 met all internal quality control criteria 12 kg lot 81 did not meet internal quality control criteria  Deviation in overall composition more than 1.5%  Not well equilibrated  Difficulties with density homogeneity foreseen (small batch size for the compacting equipment to be used)

7 Sept 2002 / 7 May 16, 2013 7 Granulates 35-45 Lot 82. Quality Certificate. Impurities The same low C contents in powder and granulate is a surpise Work ongoing to understand the reasons Powder

8 Sept 2002 / 8 May 16, 2013 8 Lot 82. Quality Certificate Powder. Filling density Powder specially agglomerated after Jet Milling to improve filling density from 0.7 to 1.5 g/cm 3 50 µ Agllomerates readily destroyed by slight pressing with~ 0.5 bar 50 µ

9 Sept 2002 / 9 May 16, 2013 9 Lot 82. Quality Certificate Grain Size Distribution Results of laser granulometry.d 50 = 1.5 µm coincide with SEM data:.d 50 = 1.7  0.2 µm Agllomerates almost destroyed by ultrasonic shaking of powder suspension in ethanol (for Laser Granulometry) Remaining aglomerates ? Flake thickness ? 1 µ

10 Sept 2002 / 10 May 16, 2013 10 XRD data Almost single-phase (Bi2212) material. Close to equilibrium:.Very small density of Bi2201 intergrowths in Bi2212 grains:. = 0.9  0.5% (powder); 1.4  0.6% (granulate)

11 Sept 2002 / 11 May 16, 2013 11 Rietveld Refinement No intergrothws => rather good fit by Rietveld refinement

12 Sept 2002 / 12 May 16, 2013 12 Rietveld Refinement. Reliability = ? Dependence of modulation structure of Bi2212 phase on cation composition and O contents is an issue for quantifying phases that are present below 1 wt %. 200,1 008,1 111,1 14-24AEC Only Bi2201 phase is determined rather reliably 113 115,1 117,1

13 Sept 2002 / 13 May 16, 2013 13 XRD Rietveld Analysis All phases except Bi2201 are in reality questionable (< 1%) The data for Bi2201 and lattice parameters are reasonable

14 Sept 2002 / 14 May 16, 2013 14 DTA/TGA data of BSCCO + 50% Ag. BSCCO (Ag) melts at 860 to 883°C Ag (BSCCO) melts at 931  0.7°C (internal reference) 100% O 2 ; 5°C/min BSCCO(Ag) Ag (BSCCO)

15 Sept 2002 / 15 May 16, 2013 15 DTA traces. Comparison with 521 Major Melting event 883  2°C (Lot 82) vs 882  1°C (Lot 521) Low-temperature event (860-880°C) is stronger in powder 82

16 Sept 2002 / 16 May 16, 2013 16 DTA traces. Powder vs Granulate Low-temperature event (860-880°C) is stronger in granulate Possible correlation with the amount of Bi2201 phase (to be studied)

17 Sept 2002 / 17 May 16, 2013 17 Tasks

18 Sept 2002 / 18 May 16, 2013 18 Motivation The rest of lot 78 acquired in January 2011 consisted of both standard (100-500 µm) and lower (< 100 µm) fractions Hypothesis: Big particles surrounded by small ones are not destroyed,.but compacted and hardened Scatter in the particle size can be detrimental Some particles are not destroyed during OPIT process W Nachtrab (2012) June 28, 2012

19 Sept 2002 / 19 May 16, 2013 19 Optimizing Particle Size Window of Granulate Three fractions produced

20 Sept 2002 / 20 May 16, 2013 20 82215123121: x20 to x50k BSE Particle vs the Grain Size x20x200 x2,5 k x1,5 k x5 k x10 k x20 kx50 k

21 Sept 2002 / 21 May 16, 2013 21 New Data from OST Hard Bi2212 particles forming when drawing wires made using granulates 78 and 80, but not using granulate Lot 77. All granulates had the same particle size window (100 to 500 µm).

22 Sept 2002 / 22 May 16, 2013 22 Formation of Hard Particles. New Hypothesis Formation of hard particles may reflect density inhomogeneity in the granules due to using different compacting technologies multiple compaction steps necessary for the required yield. when using small powder batches Quick test: Uniformity of granule response to small loads (1 to 50 bar) 82215123121 (200-500 µm) Initial After ~3 bar load

23 Sept 2002 / 23 May 16, 2013 23 Response to small Loads. Lot 80. Old lot 80 seems less homogeneous than new lot 82 8011322331 (100-500 µm) Initial After ~3 bar load 200 µ

24 Sept 2002 / 24 May 16, 2013 24 Confirmation from ESRF Granulate 82 is much more homogeneous than 80 and even 77 Inhomogeneity of lot 77 may come not from compacting but from exposure of the 3.5-year old material to environment 77162164 8221523131 8221523121 8011322331

25 Sept 2002 / 25 May 16, 2013 25 Summary Task 1 High-Quality equilibrium precursor materials  powder and  granulate with different particle size windows produced Questions for further work  Slight adjustment of composition could be advantageous for homogenizing melting behavior (suggested by DTA/TGA traces vs 2201 contents)  Modification of milling process may allow reaching low C content in just powders

26 Sept 2002 / 26 May 16, 2013 26 First Tasks

27 Sept 2002 / 27 May 16, 2013 27 Motivation Why overall composition of Bi2212 has such a strong effect on performance of round wires and tapes ? June 28, 2012 W521-524 2.14 : (2.86–x) : x :2.00 Sr/Ca = 2.25, 2.18, 1.75, 1.34 H. Miao et al 2006 Adv Cryo Eng. 52B, p. 673, (2006) [Proc. ICMC 2005]. M. Rikel et al 2006 J Phys: Conf Ser., 43 (2006) 51–54 [Proc. EUCAS 2005

28 Sept 2002 / 28 May 16, 2013 28 T c and Engineering Current Density J e (77 K, sf) vs Oxygen contents T c, K, A/cm 2  in Bi 2 Sr 2 CaCu 2 O 8+  Optimum Jc needs overdoping M. Rikel et al EUCAS 2011 June 28, 2012

29 Sept 2002 / 29 May 16, 2013 29 Data of Yamashita et al (2010) Yamashita et al (2010) studied single crystals grown from powders of B i2+x Sr 2-x Ca 1 Cu 2 cation compositions and annealed to have various O contents. They found that the crystals with smaller Sr/Ca ratio have maximum Tc at stronger overdoping levels. Though the real compositions were not measured, the Sr/Ca ratio in the 2212 phase should scale with that in the overall composition (Rikel et al 2006). Thus, our observation that maximum of Jc(  ) in round wires is at higher  than in the bulk may stem from the difference in T c (  ) for bulk (Sr/Ca = 2.45±0.02) and round wire (Sr/Ca = 2.20±0.03). We should first measure Tc of the wires. Anticipated, from Bi and Sr ionic radii measured. MR comment: Bi contents in 2212 phase should be almost constant (2.10-2.15) what is really changed is Sr/Ca ratio. This is reflected in the fall of lattice parameter Optimum DOPING depends on composition /* exact effect to be studied*/ June 28, 2012

30 Sept 2002 / 30 May 16, 2013 30 Motivation redo compositional experiments of 2004-2005 (precursor of various compositions). Conductors with different Cation Compositions may need different O doping levels for optimizing J e

31 Sept 2002 / 31 May 16, 2013 31 Task 2. Current Status and Nearest Plans Bulk rods (5 and 8 mm diameter) of Bi 2.15 Sr 2.85–x Ca x Cu 2.00 O 8+  compositions Melt Cast  DTA/TGA done. Heat Treatment designed and is under double check  XRD and SEM/EDX in progress Dip-Coated Tapes 521-524 (from OST and NSC) sent to FNAL (Tengming Shen) for Partial Melt Processing Samples, Bulk Rods & Tapes (if possible) will be annealed at NSC to vary  from 0.180 to 0.250 (*) (*) will be checked by XFA after homogenization

32 Thank you