Atomic origin of the coexistence of high critical current density and high Tc in CuBa2Ca3Cu4O10+δ superconductors
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-06-10 |
| Journal | NPG Asia Materials |
| Authors | Xuefeng Zhang, Jianfa Zhao, Huijuan Zhao, Luchuan Shi, Sihao Deng |
| Institutions | Max Planck Institute for Chemical Physics of Solids, Tsinghua University |
| Citations | 11 |
| Analysis | Full AI Review Included |
Atomic Origin of the Coexistence of High Critical Current Density and High Tc in CuBa2Ca3Cu4O10+δ Superconductors
Section titled “Atomic Origin of the Coexistence of High Critical Current Density and High Tc in CuBa2Ca3Cu4O10+δ Superconductors”Executive Summary
Section titled “Executive Summary”- Double High Performance: The CuBa2Ca3Cu4O10+δ (Cu-1234) superconductor exhibits exceptional performance, achieving both a high Critical Transition Temperature (Tc ~117 K) and a high Critical Current Density (Jc >104 A/cm2 at 100 K).
- Extrinsic Pinning Mechanism: High Jc is primarily supported by efficient extrinsic pinning centers, specifically ordered copper/oxygen vacancies and plate-like 90° microdomains, which act as dominant surface pinning centers suppressing vortex flux flow.
- Intrinsic Anisotropy Reduction: The Charge Reservoir Blocks (CRBs) [Ba2CuO3+δ] contain unique, highly compressed [CuO6] octahedra. This structure induces a large number of holes with 2pz symmetry.
- Enhanced Interlayer Coupling: The presence of 2pz holes significantly decreases the superconducting anisotropy, dramatically enhancing the interlayer coupling necessary to guarantee a high intrinsic Jc.
- Tc Maintenance in Overdoped State: High Tc is maintained despite the heavily overdoped nature of the material due to inhomogeneous carrier distribution within the thick superconducting blocks (SCBs). Inner CuO2 planes (IPs) remain near optimal doping, while outer planes (OPs) are overdoped.
- Structural Modulation: The material exhibits a clear a x 2b x 2c modulated structure, induced by the periodic ordering of vacancies, which correlates with the observed periodic lattice distortions.
- Design Applicability: These findings establish principles for designing and synthesizing new multilayered High-Temperature Superconductors (HTSCs) that successfully overcome the traditional Tc/Jc trade-off.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Critical Transition Temperature (Tc) | ~117 | K | Measured at ambient pressure (ZFC/FC). |
| Critical Current Density (Jc) | >104 | A/cm2 | Sustained at 100 K. |
| Critical Current Density (Jc) | ~5.6 x 105 | A/cm2 | At 77 K (Liquid Nitrogen Temp), Earth’s field. |
| Flux Creep Parameter (To) | 17.16 ± 0.45 | K | Jc(T) fitting at 1 T (comparable to YBCO). |
| Flux Creep Parameter (To) | 14.49 ± 0.28 | K | Jc(T) fitting at 4 T. |
| Lattice Parameter (a=b) | 3.85856(5) | Angstrom | Tetragonal basic structure (P4/mmm). |
| Lattice Parameter (c) | 17.9544(6) | Angstrom | Tetragonal basic structure (P4/mmm). |
| Average Cu Valence State | +2.29 | Unitless | Based on NPD refinement (Overdoped state). |
| Overall Hole Concentration | ~0.29 | hole/CuO2 | High carrier concentration confirmed by XAS. |
| [CuO6] Compression Ratio (σ) | 0.92 | Unitless | Ratio of out-of-plane to in-plane Cu-O bond lengths in CRBs. |
| SC Block Thickness | 0.96 | nm | Thickness of the [Ca3Cu4O8] superconducting block. |
| Microdomain Size (Longitudinal) | 100 to 500 | nm | Plate-like 90° microdomains (pinning centers). |
Key Methodologies
Section titled “Key Methodologies”Synthesis Parameters (High-Pressure Solid-State Reaction)
Section titled “Synthesis Parameters (High-Pressure Solid-State Reaction)”- Starting Materials: High-purity CaO (99.95%), CuO (99.995%), and BaO2 (95%). Handled in an argon glove box (O2/vapor < 1 ppm).
- Pressure Application: Used a cubic anvil-type high-pressure apparatus. Pressure gradually increased to 6 GPa.
- Thermal Treatment: Sample heated to 1273 K and maintained for 30 minutes, followed by cooling to ambient temperature.
Characterization Techniques
Section titled “Characterization Techniques”- Aberration-Corrected Scanning Transmission Electron Microscopy (STEM):
- Instrument: FEI Titan Cubed Themis 60-300 (300 kV), spatial resolution ≈ 0.06 nm.
- Imaging: HAADF and ABF used to visualize atomic columns and vacancy ordering (a x 2b x 2c modulated structure).
- Electron Energy-Loss Spectroscopy (EELS):
- Application: Used for orientation-dependent O-K edge measurements (probing 2pz and 2px,y orbitals) and spatially resolved layer-by-layer visualization of hole distribution.
- Neutron Powder Diffraction (NPD):
- Location: GPPD diffractometer at CSNS.
- Analysis: Rietveld refinement used to determine precise lattice parameters, atomic positions, and average Cu valence state (+2.29).
- Soft X-ray Absorption Spectroscopy (XAS):
- Application: Measured at the O-K edge to quantitatively characterize the doping level and confirm the overdoped nature of Cu-1234.
- Magnetic and Transport Measurements:
- Magnetization: SQUID magnetometer (Quantum Design MPMS3-7T) used for Tc determination (ZFC/FC).
- Jc Calculation: Derived from magnetic hysteresis loops using the Bean model, and flux creep parameters (To) were fitted.
- Strain Mapping: Geometrical Phase Analysis (GPA) applied to HAADF images to visualize periodic tensile and compressive strain induced by vacancy ordering.
Commercial Applications
Section titled “Commercial Applications”The successful coexistence of high Tc (~117 K) and high Jc (>104 A/cm2 at 100 K) provides Cu-1234 with significant potential for applications operating efficiently above the liquid nitrogen temperature (77 K) threshold.
- High-Efficiency Power Transmission: Ideal for Superconducting Power Cables (HTS cables) where high Jc is required to minimize resistive losses, allowing for operation at 77 K with reduced cooling costs compared to lower Tc materials.
- Superconducting Magnets: Applicable in high-field, high-stability magnets for advanced medical imaging (MRI), industrial separation, and high-energy physics (particle accelerators), leveraging the material’s strong flux pinning and low anisotropy.
- Magnetic Energy Storage (SMES): Suitable for large-scale energy storage systems, offering high current density capacity and improved thermal stability due to the high Tc.
- Fault Current Limiters (FCLs): The high Jc and robust performance near 100 K make Cu-1234 a strong candidate for resistive FCLs, which protect electrical grids by rapidly transitioning to a normal state during fault conditions.
- Advanced Electronic Devices: Potential for use in thin-film applications, such as high-Q microwave resonators and filters, where low anisotropy and strong interlayer coupling are beneficial for device performance.
View Original Abstract
Abstract For cuprate superconductors, a high critical transition temperature ( T c ) can be realized in compounds containing multiple CuO 2 layers in the unit cell, while a high critical current density ( J c ) is rarely sustained above liquid nitrogen temperature. The CuBa 2 Ca 3 Cu 4 O 10+δ (Cu-1234) superconductors synthesized under high oxygen pressure incredibly exhibit high T c (~117 K) and high J c (>10 4 A/cm 2 , 100 K) values. Here, the “double high” traits of Cu-1234 were investigated with advanced scanning transmission electron microscopy. It was revealed that ordering vacancies and plate-like 90° microdomains induced efficient microstructure pinning centers that suppressed vortex flux flow and enhanced J c . Furthermore, metallic charge-reservoir blocks [Ba 2 CuO 3+δ ] were composed of unique compressed [CuO 6 ] octahedra, which induced many holes with 2 p z symmetry that significantly decreased the superconducting anisotropy and dramatically enhanced the interlayer coupling that guaranteed a high J c . On the other hand, optimally doped CuO 2 planes inside the thick superconducting blocks [Ca 3 Cu 4 O 8 ] maintained a high T c . Our results are applicable to design and synthesis of new superconductors with “double high” traits.