HTS Coated Conductor Characterization and Analysis

Transcription

1 FY 9 Funding: $55 K (ORNL) $1 K (FSU) HTS Coated Conductor Characterization and Analysis 1 OAK RIDGE NATIONAL LABORATORY Presenters: Yuri Zuev, Alex Gurevich, Jim Thompson Contributors: C. Cantoni, D. K. Christen, S. Cook, A. Goyal, V. Keppens, F. A. List, M. Paranthaman, O. Polat, E.D. Specht, J.W. Sinclair, S.H. Wee, Y. Zhang Chiara Tarantini, Alex Gurevich, David Larbalestier, National High Magnetic Field Lab-FSU Y. Chen, V. Selvamanickam, SuperPower, Inc. C. Varanasi, U. Dayton/Air Force Research Lab

2 Relevance: This project directly impacts DOE Goals DOE-OE Subprogram Mission: Development of HTS wires, and novel and revolutionary electric power equipment, such as cables, fault current limiters, and transformers, utilizing HTS wires DOE-OE Subprogram Goals: Develop prototype wire achieving 1,, length-critical current (A-m) for second generation wire Produce high temperature superconducting coil that generates magnetic fields up to 5 Tesla at 65K for HTS applications Project Objectives: Provide measurement and analysis of superconducting properties to high fields for emerging materials, in order to establish the practical limits of performance Through new methodologies, define wide-range (H,T, E(J), θ) properties of short prototypes for control and applicability in real equipment Understand micro- and nano-structural factors affecting J c, per DOE Coated Conductor Technology Development Roadmap

3 FY 9 Plans 3 Develop a more complete experimental scope of the flux-pinning phenomena in systems with self-assembled extended defects Integrate angularly dependent study with wide-range characterization of E(J,θ) Determine if crossover phenomenon (~ isotropic J c ) changes strongly at much lower E-fields Implement capability for contact-free angular study as analytical tool for high value materials of special interest Advance fundamental understanding for future guidance in materials design a mechanism underlying the orientation-dependent power-law exponent α that describes J c (H) at intermediate-fields of technological relevance origin of inter-relationships among parameters describing J c (H,T,θ)

4 Presentation Outline 4 FY 9 Results Measurement and modeling of J c (H,T,θ) for improved understanding and control; extrinsic vs. intrinsic effects (Yuri) Insights into fundamental mechanisms: pinning and field (Alex) dependencies Contactless measurements and analyses of extended properties of enhanced G materials (Jim) Performance and FY 1 Plans Technology Transfer and Research Integration

5 8: Extended defects lead to unique properties of orientation-dependent critical currents c-axis θ H J c (θ) Important interplay between: Self-assembled, nd -phase columns of BaZrO 3 Intrinsic HTS anisotropy (structural, electronic) Extrinsic anisotropy induced by flux-pinning nanostructure Can lead to complex interactions and properties 5

6 8: Extended defects lead to unique properties of orientation-dependent critical currents At a given θ: 1 c-axis θ H J c H -α J c H -α J c (MA/cm ) 1.1 ~B o J c (θ) At a given field: 1 Tesla 77 K Weakly field dependent at low-field J c (H<B o ) power law dependence J c H -α (intermediate H) Rapid decay to J c at B irr <B c H (T) B irr B c Jc (MA/cm ) H columnar defects H a-b Angle from tape plane (deg) 6

7 8: Contrasts in properties: systems with ~isotropic defects dominant effects of electronic anisotropy At a given θ: 1 J c (MA/cm ) 1.1 ~B o (θ) J c H -α H (T) Weakly field dependent at low-field J c (H<B o ) power law dependence J c H -α (intermediate H) Rapid decay to J c at B irr <B c B irr (θ) B c J c (MA/cm ) 1.8 Ir-nanoparticles/STO θ 1.6 Control STO 1.4 θ c At a given field: a-b θ T = 77 K B = 1 Tesla Aside from twins, have random, isotropic pins -- mostly Y O 3 precipitates Random pinning α =.57 J c γ(θ) α m ab γθ ( ) = cos( θ) + sin( θ) mc 45 9 θ (deg) field angle from c-axis 1/ 7

8 With isotropic pins: Near-scaling of J c (H,T,θ) with B irr J c H -α 1.8 Ir-nanoparticles/STO θ 1.6 Control STO 1.4 θ c 1. 1 a-b θ J c (A/cm) K H c 15 deg 3 deg 45 deg 6 deg 75 deg H ab B/B H/B irr (θ) H/B irr Phenomenological model for orientation dependence Jc B αθ ( ) B = (1 + ) (1 ) J () B ( θ ) B ( θ ) c o irr J c (MA/cm ) B irr (Tesla) T = 77 K B = 1 Tesla Random pinning α = θ (deg) field angle from c-axis 77 K H c Irreversibility field γ(θ) m c /m ab =5 H ab θ (deg)

9 Leads to near-scaling of J c (H,T,θ) with B irr (θ) Collapse onto single curve J c H -α 1.8 Ir-nanoparticles/STO θ 1.6 Control STO 1.4 θ c 1. 1 a-b θ J c (A/cm) K H c 15 deg 3 deg 45 deg 6 deg 75 deg H ab B/B H/B irr (θ) H/B irr Phenomenological model for orientation dependence αθ ( ) J J c c () B/ B ( θ ) B irr = 1+ 1 B / B ( θ) B ( θ) o irr irr Scaling of fields with respect to B irr (θ) α nearly θ-independent Observed: α.5.69 Theory: α 5/8 for random, isotropic pins [Ovchinnikov & Ivlev, Phys. Rev. B 43 (1991)] J c (MA/cm ) B irr (Tesla) T = 77 K B = 1 Tesla Random pinning α = θ (deg) field angle from c-axis 77 K H c Irreversibility field γ(θ) m c /m ab =5 H ab θ (deg)

10 With columnar pins: Isotropic phenomenon in J c (H,θ) 1 For field orientations < θ < 9 : near isotropic J c at B*(T)! Jc B α θ B = (1 + ) (1 ) J () B ( θ ) B ( θ ) ( ) c o irr B*.8 μm thick H c c-aligned columns H ab α B o (mt) θ (deg) B*= Tesla K H ab 3 1 c ab B irr (Tesla)

11 Inter-relationships among observed parameters 11 monotonic α(θ) (with weak temperature dependence) crossover field B*(T) scales with B irr (T) New kind of scaling: all J c (H,T,θ) should fall inside envelope Usefulness depends on materials control of B* (through α, B o B irr ) α J c /J c (H=) sample B sample A Angle θ (degrees) H c B (T) B* (T) 1. T = 65, 7, 74, 77, 8 K 15 1 H/H irr,c B irr,c (T) K 77K 74K 7K 65K H ab T (K) [APL 93, 1751 (8)] B * B irr,c T c

12 9: Measured high-field B irr (θ) from resistive transitions in field 1 NdBa Cu 3 O 7 + vol% BaZrO 3 with columnar defects Measured B irr are less anisotropic than B melt γ(θ), due to CDs [previously observed, e.g., by Baily et al., PRL 1 (8)] 3.5 Near-scaling common high-t dependence B irr Birr/Birr,c (θ)/b irr,c T = 7, 74, 77, and 8 K [Florida State University (NHMFL) collaboration] γ = 5 γ = 7.8 μm thick H c θ (deg) theta (deg) H ab

13 Use measured B irr (θ) and model ideal α(θ) 13 Apply measured B irr (θ) to invert model: αθ ( ) = ln (1 */ ( )) irr θ / ln(1 + B* / Bo ( θ)) B B j Constrain B* and J c (B*) to values experimentally observed ideal α [illustrated at 77 K; scaling yields equivalent results at other T] o B Irr ( Tesla ) Jc/Jco B//c T = 77 K θ θ B//ab K θ= H c θ ( degrees ) Jc B α B = (1 + ) (1 ) J () B B ( θ) c o irr (a) H (Tesla) θ=9 H ab (c) α J c (MA/cm ) (b).1 T = 65, 7, 74, 77, and 8 K θ o T c =9.3 K 77 K B* H (Tesla) (d)

14 9: Asymmetry in properties of HTS on IBAD templates 14 Jc (MA/cm ) H to: Tesla 77 K (YGd)BCO + BZO 1 Tesla 77 K < 9 H columnar defects Angle from tape plane (deg) tape normal (YGd)BCO + BZO H a-b tape plane J c (MA/cm ) (YSm)BCO + BZO.6 < Tesla 77 K B θ (degrees) (YGd)BCO + BZO 1 Tesla 77 K Ic (A) < 9 J c (MA/cm ) H to: tape normal Angle from tape plane (deg) tape plane

15 15 9: Asymmetry in properties of HTS on IBAD templates Different J c crossing phenomena observed in different orientation quadrants [Can be described with pinning model by interplay between B o (θ) and α(θ)] 1 Single crossing SHA1171,.8μm YBCO + Ta metal Peaks far apart T=65K Double crossing Peaks close together J C (MA/cm ) 1.1 J C (MA/cm ) T=77K Angle % (degrees) (?X) H H(T) J C (MA/cm ) B* Angle(degrees) % H (?X) (T)

16 9: Asymmetry in properties of HTS on IBAD templates 16 Flux pinning is symmetric with tape for current transverse to tape axis H to: tape plane 1 Tesla 77 K 3 also, Maiorov et al., Appl. Phys. Lett. 86 (5) longitudinal n transverse J c (MA/cm ) tape normal I longitudinal I transverse

17 9: Asymmetry also observed in irreversibility field 17 H Irr (Tesla) tape T = 77 K 16T machine T = 8 K T = 84 K 77K, 3T machine 74K, 3T machine tape Scaling is incomplete near position of columnar defects tape θ ( degrees ) H irr /H irr, min Further underscores effects of flux pinning on B irr (not limited by vortex melting) T = 77 K 16T machine T = 8 K T = 84 K 77K, 3T machine 74K, 3T machine tape BZO columns 1. tape tape θ (degrees)

18 Asymmetries are consistent with lattice and nanostructural tilts18 Longitudinal views HTS lattice tilts from plane of tape by ~3 (YSm)BCO + BZO 5 nm (YGd)BCO + BZO a-b planes Surface normal 9 15 In addition to splay, materials can have a statistical tilt of columnar defects from HTS lattice

19 Lattice and nanostructural asymmetries and tilts are absent in transverse view 19 Columns exhibit splay, but on average are aligned with tape (net tilt is only into or out of the image plane) Consistent with observed symmetric J c (θ) Transverse views 5 nm (YGd)BCO) + BZO

20 Schematic representation of tilted structures: consistent with observed pinning peaks The lattice grows with~-3 tilt from the plane of the tape (due to epitaxial growth on IBAD-tilted buffers) The BZO columns grow tilted from both the lattice and tape RE-oxide platelets grow both tilted from and aligned with a-b planes Longitudinal cross-section counts / sec counts / sec LMO buffer LMO() Δω =.47 tilt = omega (deg) R O 3 YO3(4) Δω = 1.88 tilt =.37 counts / sec counts / sec BZO() Δω =.17 tilt = omega (deg) BZO RBCO YBCO(5) Δω = 1.3 tilt =.34 XRD shows all phases coherent with HTS lattice and oriented ~ from tape omega (deg) omega (deg) [Y. Zhang et al., Physica C (in press)]

21 Summary: 1 For strong-pinning extended defects, can have J c (B*,θ)~constant The effect is due to competition between anisotropies: extrinsic due to strong, correlated pinning (small power-law α near H c) intrinsic due to electronic anisotropy (although B irr is also affected by pinning) High-field measurements of B irr (θ): less anisotropic than electronic anisotropy and B melt γ(θ) show consistency of pinning model Asymmetric orientation-dependent pinning on IBAD templates lattice and defects arrays are tilted from the tape template asymmetric pinning also affects B irr Materials control and understanding of fundamental inter-relationships (α, B o, B irr,nanostructure) is crucial for optimal wire development

22 Presentation Outline FY 9 Results Measurement and modeling of J c (H,T,θ) for improved understanding and control; extrinsic vs. intrinsic effects (Yuri) Insights into fundamental mechanisms: pinning and field (Alex) dependencies Contactless measurements and analyses of extended properties of enhanced G materials (Jim) Performance and FY 1 Plans Technology Transfer and Research Integration

23 Understanding correlated pinning: can pinning texture produce isotropic J c (H) in anisotropic YBCO? 3 New pinning physics brought by spatial correlation of nanoprecipitates: self assembled BZO chains of nanoparticles or nanorods. Measurements of the angular dependencies of J c and H irr at high dc fields, up to 3 T at NHMFL, done by Chiara Tarantini. Development of a self-consistent theory, which incorporates spatial correlations of pinning defects to understand the angular dependencies of J c and H irr Can correlated pinning make both J c and H irr isotropic? How far can the irreversibility field be increased by nanoprecipitates?

24 High field measurements of H irr K 74 K K 74 K 7 μ H Irr ( Tesla ) H Irr /H Irr. (θ=45 ) θ ( degrees ) θ ( degrees ) Good angular scaling for 77 and 74 K

25 Does Ginzburg-Landau (GL) scaling for H irr work? 5 36 GL curve with γ Ηc = GL with a single parameter γ cannot fit the data μ H Irr ( Tesla ) GL γ Ηc =.3 H c is a better measure of the electronic anisotropy H irr ( θ ) H irr = () cos θ + γ sin θ 6 77 K θ ( degrees )

26 Reduced anisotropy of H c 6 μ H ( Tesla ) % R N 99% R N GL scaling for H c works well Fitting from 1 to 17 Data: Hc_C Model: Anisotropy Weighting: y No weighting γ extracted from the GL scaling is reduced from 5 to 3 γ High density of nanoparticles seems to reduce the electronic anisotropy of YBCO Chi^/DoF =.513 R^ = P1.164 ±.78 P ±.6363 Fitting all the data from 1 to 6 Data: Hc_C Model: Anisotropy Weighting: y No weighting Chi^/DoF =.131 R^ = θ ( degrees ) P ±.39 P.8988 ±.686

27 How can the anisotropy of H c be reduced? 7 Meandering ab planes due to strong strains caused by dense nanoprecipitate structures and misaligned grains Averaged H c over the angular spread of the meandering ab planes ~ H c ( θ ) = π / H c() F( α) dα π / sin ( θ + α) + γ cos ( θ + α) A vortex probes randomly oriented ab planes

28 Anisotropy of J c in the collective pinning theory 8 Vortices bend to accommodate pins J c for a vortex segment of the Larkin correlation length L c J c U φ n 4 / 3 / 3 p p 1/ 3 1/ 3 ε rp, (Larkin and Ovchinnikov, 1973) J c ( H, θ ) = J ( Hε ), c θ ε θ = cos θ + γ sin θ Anisotropic scaling rule: (Blatter et al, 1994) Vortex line tension is minimum along the ab planes: J c (θ) is maximum Pinning correlation function: F(r r / ) = F δ(r r / ) does not take Into account any spatial correlations of pins

29 Mechanisms of anisotropy of J c 9 1. Anisotropy of the vortex line tension due to electronic anisotropy (taken into account by the collective pinning theory). Anisotropy of the vortex interaction with pinning centers: - shape anisotropy of pins (oblate or nanorod precipitates) - anisotropy of core and magnetic interaction of a vortex with pins 3. Texture in the pinning potential: correlated self-assembled chains of nanoprecipitates 4. Splay in the angular distribution of chains

30 3 Correlation function of pinning forces Pin density correlation function >= =< / 3 exp () ) ( ) ( c a c a i r z r r r n n R n R S ρ π δ δ 3/ 3 ) ( ) (, exp ) ( r r f r f f p + = ρ ε ρ ρ ρ Long range magnetic pinning force (pore of radius r ) Short range core elementary pinning force Elementary pinning interactions )] ( )exp[ ( ) ( ) ( ) ( ) ( ) ( / 3 3 / r r ik k S k f k f k d r F r F r r r r r r v r >= < β α β α π

31 Strong vortex pinning 31 Strong pinning destroys vortex lattice. Pinning of vortex lines confined by magnetic cage potential from other vortices r u r r r ε K u + F u, z ) = z J φ xˆ ( Cage spring constant K and the line tension of the vortex ε in the nonlocal limit of small dense pins r a << λ: K = φ H 8πλ ε = 1 γ φ 4πλ A self consistent mean field theory of vortex depinning has been developed to take into account realistic pinning correlation functions Anisotropy of the pinning potential can be included to calculate the orientational dependence of J c

32 3 Field dependence of J c (H) for H c Account for the finite correlation radii in the pinning structure + + = 3 4 ) ( ) / exp( 8 ) ( R K q dq r q e r n r H J c a i c ε φ ε R is determined by the self-consistency equation 4 ) / ( 8 a i r r n R K R γ π = + for pores of radius r << r a For H = and r c =, the equations reduce to the collective pinning result for uncorrelated point pins Generalization to tilted magnetic fields

33 Domains of different field dependences of J c (H) Low field: J c (H) J(), for H < H. Intermediate field: H I < H < H 1 : J c H -1/ 3. Strong fields : H > H 1 : J c H -1 Thermal activation of vortices is not included: H << H irr Upper crossover field H 1 φ /r c γ Lower crossover field: H I φ (γn i /π ) /3 (r /r a ) 8/3 For precipitates of radius r 4 nm, and r a n i -1/3 nm, γ = 5, the lower crossover field H.3 T The upper crossover field, H 1 T for r c 1 nm, γ = 5.

34 Field dependence of J c and the α parameter 34 Gradual increase of α(h) as H increases

35 Presentation Outline 35 FY 9 Results Measurement and modeling of J c (H,T,θ) for improved understanding and control; extrinsic vs. intrinsic effects (Yuri) Insights into fundamental mechanisms: pinning and field (Alex) dependencies Contactless measurements and analyses of extended properties of enhanced G materials (Jim) Performance and FY 1 Plans Technology Transfer and Research Integration

36 8: Develop tools to obtain wide-range superconductive properties with H c-axis: apply different experimental methods Electrical transport V Log(E/E c,t ) E ~ J n ; n>>1 36 J t <J c,t E t (J t /J c ) n >1-7 V/cm Field-sweep magnetometry dh/dt Transport J c criterion J Log(J/J c,t ) c,t J c,t magnetic measurements Needed operation criterion I op /I c E fs dφ/dt dh/dt (J/J c ) n ~ V/cm Flux-creep (current decay) magnetometry E fc dφ/dt dj/dt (J/J c ) n ~ V/cm E(J)

37 8: devised & qualified contact-free measurements of J c (H,T,θ) 37 Measure longitudinal and transverse components of magnetic moment in Quantum Design SQUID magnetometer. Coated conductor Transverse pickup coils (striated), with rotation about horizontal axis. m Longitudinal pickup coils H to SQUID sensor m [Thompson et al, SuST invited issue (submitted)] magnetic moment m (G-cm 3 ) Magnetization loops for m and m m m Superpower #1,.7 μm T = 5 K θ = 65 deg H (koe)

38 38 In-depth study on SuperPower 1.6 μm (Sm-Y)BCO, with BaZrO 3 columnar defects, (RE)-oxide precipitates, and point-like disorder c-axis ab-planes

39 9: the angularly dependent current density J c evolves remarkably as T decreases 39 J c (1 6 A/cm ) J c (1 6 A/cm ) H = 1 T H = 3 T T = 5 K T = 5 K K 35 K 5 K 65 K K 35 K 5 K 65 K θ (angle from surface normal) T = 5 K K 35 K 5 K 65 K H = 1 T 77 K T = 5 K K H = 3 T 35 K 5 K 65 K θ (angle from surface normal) The electric field E is very low, V/cm, in all these contact-free measurements.

40 At lower temperatures (here 35 K), J c (θ) in high fields varies little with angle. 4 J c (MA/cm ) 1 T = 35 K = 3 % Oe koe 4 koe 6 koe 8 koe 1 koe 15 koe koe 5 koe 3 koe 35 koe 4 koe 45 koe 5 koe θ c (degrees)

41 The in-plane J c (θ) becomes isotropic & is large (.6 MA/cm ) in high field 41 J c (MA/cm ) 1 T = K θ c (degrees) Oe koe 4 koe 6 koe 8 koe 1 koe 15 koe koe 5 koe 3 koe 35 koe 4 koe 45 koe 5 koe 55 koe 6 koe What is the physical origin of this isotropic crossing phenomenon?

42 Physically, ~ isotropic J c (θ) can originate from combined action of different pinning centers with opposite angular dependencies 4 Partition the current densities into weak + strong components, after J. Plain et al., PRB 65 (): T T J ( T; H) = J e + J e / 3( T/ T*) c wp cd (Note - splay of CDs can enhance their contribution at high temperatures.) J c (MA/cm ) T, H c Weak+Strong fit Strong comp Weak comp Chi^/DoF = 1.9E9 R^ = Jwp 8.88E6 ± 1.E6 T 13.5 ± 4.4 Jcd 4.8E6 ± 1.6E6 Tstar 75. ± 3.5 Minimum For H c Maximum for H CD Point disorder dominates J c (1 6 A/cm ) H = 3 T T = 5 K K 35 K 5 K 65 K θ (angle from surface normal) T (K) H = 3 T T = 5 K K 35 K 5 K 65 K θ (angle from surface normal) Correlated disorder dominates

43 α-values also reflect multiple contributions to pinning, comparing low versus high T 43 SP M3-53-5, 1.6 μm striated; G/s 1 J c (MA/cm ) K, deg 1 K, deg K, deg 3 K, deg 4 K, deg 5 K, deg 6 K, deg 65 K, deg 71 K, deg 77 K, deg 8 K, deg.8 SP M3-53-5, 1.6 μm striated; G/s H (T) α H > 1 T H < 1 T T (K)

44 9: construct E(J) for wide range of dissipation, T, H, and now orientation θ 44 transport swept field db < E ( 1 swept > ) a dt E (V/cm) current decay dj < E ( 1 creep > 8 ) adμ, dt a = strip width, d = thickness 1E-5 1E-6 1E-7 1E-8 1E-9 1E-1 1E-11 1E-1 1E-13 1E-14 θ = n = J (MA/cm ) (T, H, θ ) 74K, 1T, deg 71K, 1T, deg 65K, 1T, deg 6K, 1T, deg 5K, 1T, deg 4K, 1T, deg 3K, 1T, deg K, 1T, deg 5K, 1T, deg 77K, 1T, deg 77K, 1T; J cd 65K, 1T; J cd A power law dependence, E ~ J n, is observed over a wide range of temperature and dissipation. The index n ~ (1/S) increases as the temperature is reduced. Contact-free tools: facile for high performance materials (and complement transport) no sample burnout, self-limiting currents, no issues of heating at contacts get properties of lab-scale samples at low dissipation, realistic levels not usable presently for H ~ parallel to tape surface

45 9: find E(J) at low dissipation & broad T range, with θ = 45 1E-1 1E-11 θ = ; T (K) E (V/cm) 1E-1 1E-13 1E J (MA/cm )

46 9: find E(J) at low dissipation & broad T range, with θ =, 3 46 E (V/cm) 1E-1 1E-11 1E-1 1E-13 θ = ; T (K) θ = 3; T (K) E J (MA/cm )

47 9: find E(J) at low dissipation & broad T range, with θ =, 3, and E (V/cm) 1E-1 1E-11 1E-1 1E-13 1E J (MA/cm ) θ = ; T (K) θ = 3; T (K) θ = 45; T (K)

48 As H decreases, position of peak in J c (θ) shifts away from c-axis and orientation of (tilted) CDs 48 Contrast BaSnO 3 CDs substrate [Varanasi et al., APL (8)] with tilted BaZrO 3 CDs SuperPower M3 material J c (MA/cm ) J c (MA/cm ) Oe koe.4 4 koe 6 koe. 8 koe 1 koe. 15 koe koe 5 koe 4. 3 koe koe (b) 4 koe koe.5 T = 65 K 5 koe (a) T = 65 K H c-axis θ (angle from surface normal) θ peak (degrees) Can explain many features in terms of misalignment between external field H and internal field B CD. [Silhanek, Civale, PRB ()] But pinning landscape is complex; other types of defects may have significant impact K 5 K 65 K 77 K h -1 = H c (θ,t)/h

49 Other recent SP materials exhibit similar features in J c (H,T), creep rate 49 3 SP-M1-1975, from creep study.1 creep rate S(T) for H = 1 T, perp plane J c (MA/cm ) T, deg Weak+Strong fit strong comp weak comp Chi^/DoF = 18E9 R^ =.9987 Jwp 1.99E7 ±.7E6 T 16. ±4.6 Jcd 7.96E6 ±3.3E6 Tstar 83.6 ±4.1 S SP-M1-1975; BZO PV318A; BSO Temperature (K) I c = 996 A/cm at 76 K, sf Temperature (K) The BSO-doped mat l with dominant CD pinning [Varanasi, APL (8)], has a peak in S(T) near 3 K due to VRH of vortices. [Thompson, PRL (1997)]. In the SuperPower HTS, there is no peak, showing that multiple defect types suppress depinning. [Maiorov, Nature Mater (9)].

50 J c (MA/cm ) 1.1 Apply tools to help SuperPower optimize & understand Zr-addition in.4 μm HTS SuperPower 155 series (.4 μm thickness) H =.1 T.5 T.5 T 1 T T J c (MA/cm ) 1 SuperPower 155 series (.4 μm thickness) T = 4 K H =.1 T.5 T.5 T 1 T 3 T 5 T 5.1 T = 77 K Zr added (at %) J c (MA/cm ) SuperPower 155 series (.4 μm thickness) T = 5 K H =.1 T.5 T.5 T 1 T 3 T 5 T Zr addition (at %) The same Zr-level gave a maximum J c for a wide range of fields and temperatures Zr addition (at %)

51 Similarly characterize SP Zr-doped mat l from production reactor: 7.5 % Zr-add n 51 J c (MA/cm ) H = 1 T Jc (MA/cm^) Weak+Strong fit weak comp strong comp Data: M311kOe_Jc Model: WeakStrongPin Weighting: y No weighting Chi^/DoF = 16E9 R^ = Jwp 1.5E7 ±5.79E6 T 18.7 ±1.8 Jcd 5.9E6 ±6.68E6 Tstar 86. ±8.93 J c (MA/cm ) H = 6 T Jc (MA/cm^) Weak+Strong fit weak comp strong comp Data: M316kOe_Jc Model: WeakStrongPin Weighting: y No weighting Chi^/DoF = 19.9E9 R^ = Jwp.8E6 ±1.39E6 T.9 ±7.9 Jcd 3.3E6 ±1.45E6 Tstar 7.4 ± Temperature (K) Temperature (K) Qualitative trend the strong pinning component from correlated disorder becomes increasingly dominant, over larger T range, as H increases.

52 9: Investigate changes in H irr and creep with thickness d =.7.8 μm, for sequentially deposited series of SP tapes, with no BZO (columnar) defects 5 S=dln(J)/dln(t) μm 1.4 μm.8 μm H app = 1 T T (K) S=-dln(J)/dln(t) μm 1.4 μm.8 μm H app = 3 T For thinner conductor, the creep rate S diverges at a lower temperature => persistent current J collapses => system hits H irr (for E criterion 1 11 V/cm) J c (MA/cm ) Superpower (Gd-Y)BCO, Laser Scribed Edges T = 77 K thickness J c (MA/cm, sf).7 μm μm. T (K) H (Oe)

53 9: analyze and model E(J) for same series of SP tapes (no Zr-based defects) 53 Experiment: combine transport, swept field magnetization, and creep studies. current decay transport swept field E (V/cm) E-5 1E-6 1E-7 Modeled E(J) 5 K K 4 K 55 K 65 K 7 K 77 K 1E-8 1E-9 1E-1 1E-11 1E-1 1E-13 1E J c *d (A/cm) μ H app =1 T thickness=.8 μm

54 9: analyze and model E(J) for same series of SP tapes (no Zr-based defects) 54 Experiment: combine transport, swept field magnetization, and creep studies. Model: treat system as a thermally activated glassy superconductor. J ( T, t) = J μk BT 1 + U c ln t t 1 μ U = pin energy scale, from AK creep at low T μ = glassy exponent, from Maley analysis 1/t = hopping attempt frequency, from plateau in creep rate S J c (T) = current density without thermally activated decay (fitted) π ad dj < EJ ( ) >= 1 dt E (V/cm) E-5 1E-6 1E-7 Modeled E(J) 5 K K 4 K 55 K 65 K 7 K 77 K 1E-8 1E-9 1E-1 1E-11 1E-1 1E-13 1E J c *d (A/cm) μ H app =1 T thickness=.8 μm

55 9: analyze and model E(J) for same series of SP tapes (no Zr-based defects) 55 Experiment: combine transport, swept field magnetization, and creep studies. Model: treat system as a thermally activated glassy superconductor. J ( T, t) = J μk BT 1 + U c ln t t 1 μ U = pin energy scale, from AK creep at low T μ = glassy exponent, from Maley analysis 1/t = hopping attempt frequency, from plateau in creep rate S J c (T) = current density without thermally activated decay (fitted) π ad dj < EJ ( ) >= 1 dt E (V/cm) E-5 1E-6 1E-7 Modeled E(J) 5 K K 4 K 55 K 65 K 7 K 77 K 1E-8 1E-9 1E-1 1E-11 1E-1 1E-13 1E J c *d (A/cm) μ H app =1 T thickness=.8 μm

56 9 technical progress: contact-free characterization 56 Angularly dependent Jc evolves qualitatively with temperature and field, due to vortex pinning by differing defect morphologies. This combination gives large, ~ isotropic J c in multi-tesla fields at lower temperatures. Low dissipation E(J) studies have been expanded into angular domain. Wide set of SP materials have similar features (partitioning of J, creep rate vs T, ) => findings from detailed studies have more general applicability. Can model E(J) curves using a few parameters from creep experiments; varying the thickness (.7.8 μm) gives only modest changes, < 15 %, in parameters. Increasing the thickness reduces J c (by ~ 3 %), but increases H irr.

57 Presentation Outline 57 FY 9 Results Measurement and modeling of J c (H,T,θ) for improved understanding and control; extrinsic vs. intrinsic effects (Yuri) Insights into fundamental mechanisms: pinning and field (Alex) dependencies Contactless measurements and analyses of extended properties of enhanced G materials (Jim) Performance and FY 1 Plans Technology Transfer and Research Integration

58 FY 9 Plans Results 58 Develop a more complete experimental scope of flux-pinning phenomena in systems with selfassembled extended defects Advance fundamental understanding for future guidance in mateials design Integrated angularly dependent and wide-range characterization Implemented methodology for contact-free characterization of orientation-dependent J c Established evolution of orientation dependence at low (practical) electric field levels Showed inter-relationships between intrinsic and extrinsic anisotropy can appropriately model behavior of strong-pinning materials Measured H irr (θ) and H c (θ) to 3 T. Developed self-consistent theory for correlated pinning; identified one mechanism that can reduced apparent electronic anisotropy

59 FY 9 Plans Results 59 Assist SuperPower in understanding and optimizing Zr-doping levels of HTS coatings Showed that same Zr addition optimizes properties for a wide field and temperature range

60 FY 1 Plans 6 Develop a more complete experimental scope of the observed flux-pinning phenomena in systems that exhibit the combined effects of self-assembled extended and additional pinning structures Further advance the level of fundamental understanding for future guidance in materials design: Define mechanisms that underlie the observed regimes of field- and orientation-dependent critical currents guide wire development for tuning of near-isotropic J c (θ) to desired field-temperature regions Introduce effects of thermal activation into theoretical analyses Apply the newly developed methodologies to establish properties of supercurrent conduction in coated conductors at the lower temperatures, high magnetic fields, and low electric field regimes where G-wire based equipment and devices may be operated. Extend high field measurements at NHMFL to 45 Tesla

61 Technology Transfer and Research Integration 61 Technology Transfer and Impact: Transfer of ORNL J c (H,T,θ) findings to SuperPower; evaluate doping effects to make SP tapes more consistent and uniform HTS properties characterization of innovative, SSIFFS (sapphire fibers) approach to coated conductors [see ORNL talk Strategic Substrate Development for Coated Conductors ] Identify sources and quantify non-superconductive hysteretic losses in AMSC laminated tapes Industrial/Lab partnerships and interactions with: SuperPower: G research materials for properties studies; templates for HTS coatings investigations Air Force Research Lab: YBCO coatings with self-assembled BaSnO 3 nanocolumns; collaborative studies National High Magnetic Field Lab: project inspired comprehensive high field studies of coated conductors, combined with theoretical development

62 Technology Transfer and Research Integration (cont d) 6 Integration with and contributions from academic collaborations: Univ. Tennessee: Profs. Jim Thompson and Veerle Keppens, Research Asst. Prof. S. H. Wee, two post-docs & two students conducting properties characterization NHMFL-FSU: Profs. D. Larbalestier and A. Gurevich, and post-docs C. Tarantini and F. Kametani N. Carolina A&T Univ.: Prof. D. Kumar providing access and expertise for field-sweep magnetization experiments ORISE: post-doctoral associates offer invaluable technical support 5 Presentations, 7 refereed articles, and R&D 1 Award