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 | Chinese Academy of Sciences, State Key Laboratory of New Ceramics and Fine Processing |
| Citations | 11 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: High-Performance Superconductors
Section titled “Technical Documentation & Analysis: High-Performance Superconductors”Executive Summary
Section titled “Executive Summary”This research successfully synthesized and characterized the CuBa₂Ca₃Cu₄O₁₀+δ (Cu-1234) superconductor, demonstrating exceptional “double high” performance critical for next-generation high-power applications.
- Record Performance: Cu-1234 exhibits a high critical transition temperature ($T_c$) of $\sim 117$ K and a high critical current density ($J_c$) of $5.6 \times 10^5$ A/cm2 at 77 K, significantly exceeding most Bi-based cuprates.
- Intrinsic Pinning Mechanism: The high $J_c$ is attributed to efficient surface pinning centers induced by ordered copper and oxygen vacancies, forming plate-like 90° microdomains.
- Structural Origin of Low Anisotropy: The charge-reservoir blocks contain highly compressed [CuO₆] octahedra, which induce holes with $p_z$ symmetry, dramatically decreasing superconducting anisotropy and enhancing interlayer coupling.
- Inhomogeneous Doping Strategy: The material maintains high $T_c$ in a heavily overdoped state through inhomogeneous carrier distribution, with outer CuO₂ planes (OPs) being overdoped and inner planes (IPs) maintaining near-optimal doping.
- Application Potential: The results provide a crucial blueprint for designing new multilayered superconductors with coexisting high $T_c$ and high $J_c$, suitable for high-power applications above liquid nitrogen temperature.
- 6CCVD Relevance: The integration of such high-performance materials into practical devices necessitates substrates with extreme thermal management capabilities, a core specialty of 6CCVD’s MPCVD diamond products.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the synthesis and characterization of the Cu-1234 superconductor:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Critical Transition Temperature ($T_c$) | $\sim 117$ | K | Measured via magnetization (ZFC/FC) at 30 Oe. |
| Critical Current Density ($J_c$) (77 K) | $5.6 \times 10^5$ | A/cm2 | Calculated using the Bean model in Earth’s field. |
| Critical Current Density ($J_c$) (100 K) | $1.7 \times 10^5$ | A/cm2 | Demonstrates high potential near 100 K. |
| Synthesis Pressure | 6 | GPa | Applied using a cubic anvil-type high-pressure apparatus. |
| Synthesis Temperature | 1273 | K | Maintained for 30 minutes. |
| Average Copper Valence State | +2.29 | N/A | Based on NPD refinement of Cu0.94Ba₂Ca₃Cu₄O10.66. |
| Tetragonal Lattice Parameter (a=b) | 3.85856(5) | Å | Determined by Neutron Powder Diffraction (NPD). |
| Tetragonal Lattice Parameter (c) | 17.9544(6) | Å | Determined by Neutron Powder Diffraction (NPD). |
| [CuO₆] Octahedron Compression Ratio ($\sigma$) | 0.92 | N/A | Ratio of out-of-plane to in-plane Cu-O bond lengths ($d_{out-of-plane}/d_{in-plane}$). |
| Flux Creep Parameter ($T_o$) (1 T) | $17.16 \pm 0.45$ | K | Fitting parameter for $J_c(T) = J_c(0)exp(-T/T_o)$ below 60 K. |
| TEM Sample Thickness | < 20 | nm | Prepared via argon ion beam milling. |
Key Methodologies
Section titled “Key Methodologies”The research relied on high-pressure synthesis and advanced, aberration-corrected electron microscopy techniques to resolve atomic structure and electronic properties.
- High-Pressure Solid-State Synthesis: Cu-1234 bulk samples were synthesized from high-purity starting materials (CaO, CuO, BaO₂) under argon gas in a glove box. The reaction was performed at 6 GPa pressure and 1273 K temperature using a cubic anvil-type high-pressure apparatus.
- Cross-Sectional TEM Specimen Preparation: Samples were prepared using standard mechanical grinding, tripod polishing, and argon ion beam milling in a liquid nitrogen-cooled stage to achieve ultra-thin specimens (< 20 nm).
- Aberration-Corrected STEM Imaging: Atomic scale structures were studied using an FEI Titan Cubed Themis 60-300 (300 kV) with a spatial resolution of $\approx 0.06$ nm, employing High-Angle Annular Dark Field (HAADF) and Annular Bright Field (ABF) methods.
- Structural Refinement: Neutron Powder Diffraction (NPD) data, obtained from the China Spallation Neutron Source (CSNS), was analyzed using the Rietveld method (GSAS/EXPGUI package) to determine lattice parameters and chemical composition.
- Electronic Structure Analysis: Soft X-ray Absorption Spectroscopy (XAS) and orientation-dependent STEM-Electron Energy Loss Spectroscopy (EELS) were used to characterize the O-K edge, revealing hole symmetry ($p_z$ vs. $p_{x,y}$) and inhomogeneous carrier distribution.
- Superconducting Property Measurement: Magnetic susceptibility ($T_c$) and magnetization hysteresis loops ($J_c$) were measured using a SQUID magnetometer (Quantum Design MPMS3-7T).
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The development of high-performance materials like Cu-1234, particularly for high-power applications, requires integration onto substrates that can manage extreme thermal loads and provide ultra-flat surfaces for thin-film growth. 6CCVD’s MPCVD diamond is the ideal enabling material for this research trajectory.
Applicable Materials
Section titled “Applicable Materials”The primary challenge in scaling HTSC devices is thermal management and structural integration. 6CCVD offers materials tailored to meet these demands:
- Optical Grade Single Crystal Diamond (SCD): Required for applications demanding the absolute highest thermal conductivity ($\sim 2200$ W/mK) to dissipate heat generated during high-current operation, ensuring device stability and performance near 77 K.
- High-Purity Polycrystalline Diamond (PCD): Ideal for large-area integration and cost-effective scaling. Our PCD wafers offer excellent thermal properties and are available in large dimensions, suitable for thin-film deposition of complex oxides like Cu-1234.
- Boron-Doped Diamond (BDD): If the research expands into using diamond as an active electrode or conductive layer, 6CCVD provides heavily Boron-Doped Diamond films with tunable conductivity.
Customization Potential
Section titled “Customization Potential”The research involves atomic-scale structural control and implies future device fabrication (thin films, microdomains). 6CCVD’s customization capabilities directly support the transition from bulk synthesis to integrated devices.
| Research Requirement | 6CCVD Capability | Technical Specification |
|---|---|---|
| Large-Area Scaling | Custom Dimensions | PCD plates/wafers available up to 125 mm diameter. |
| Thin-Film Growth Template | Polishing & Surface Quality | Ultra-low roughness polishing: Ra < 1 nm (SCD), ensuring the necessary template flatness for epitaxial growth of complex oxide films. |
| Thermal Management | Substrate Thickness | SCD/PCD wafers available from 0.1 µm to 500 µm for thin films, and robust substrates up to 10 mm thick for high-power heat spreading. |
| Device Contacting | Custom Metalization | In-house capability for depositing standard electronic contacts (e.g., Ti/Au, Pt/Au) or refractory metals (W, Cu) directly onto diamond surfaces. We offer Au, Pt, Pd, Ti, W, Cu metalization services. |
| Global Supply Chain | Shipping & Logistics | Global shipping available (DDU default, DDP available) to ensure rapid delivery to international research facilities. |
Engineering Support
Section titled “Engineering Support”The complexity of integrating novel HTSCs like Cu-1234 requires deep material science expertise. 6CCVD’s in-house PhD team specializes in optimizing diamond material properties (crystallinity, orientation, doping, and surface termination) for advanced electronic and quantum applications. We can assist researchers in selecting the optimal diamond grade and surface preparation method to maximize the performance and stability of Cu-1234 thin films or micro-devices.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
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.