Key Takeaways & Executive Findings
- •• • RE3TaO7 ceramics exhibit hardness (H) of 5.8–14.9 GPa and elastic modulus (E) of 127.5–247.8 GPa, enabling resistance to high-speed particle impact and thermal stresses in TBC applications. • • Fracture toughness (KC) of RE3TaO7 ranges from 1.0 to 2.0 MPa·m1/2, exceeding RE2Zr2O7 (1.0–1.5 MPa·m1/2), due to weberite structure promoting crack deflection and energy dissipation. • • Wear resistance parameter MDP (0.55–0.67) for RE3TaO7 is superior to RE2Zr2O7, indicating enhanced durability in abrasive environments. • • The selection of KC calculation method depends on l/α ratio: Eq. (3) for l/α < 1 and Eq. (4) for l/α > 1; the indentation energy method is invalid for brittle ceramics due to cracking, ensuring accurate mechanical property assessment.
Abstract
Comprehensive mechanical properties, including hardness (H), elastic modulus (E), fracture toughness (KC), and wear resistance, are essential for oxide ceramics used in demanding environments. This work employs nanoindentation to evaluate these properties for RE3TaO7 (RE=La, Sm, Eu, Gd, Dy, Lu) and identifies the optimal calculation method for KC in brittle oxide ceramics. The ratio of indentation crack length to half-diagonal (l/α) is a key parameter: Eq. (3) is suitable when l/α < 1, while Eq. (4) applies when l/α > 1. The indentation energy method is invalid for brittle ceramics due to crack formation at high loads. RE3TaO7 oxides exhibit H of 5.8–14.9 GPa, E of 127.5–247.8 GPa, and KC of 1.0–2.0 MPa·m1/2, surpassing RE2Zr2O7 (KC 1.0–1.5 MPa·m1/2). Wear resistance, indicated by MDP, ranges from 0.55 to 0.67, outperforming RE2Zr2O7. The superior fracture toughness is attributed to weberite structure with crack deflection and tortuous propagation, contrasted with pyrochlore's straight cracks. These findings provide accurate nanoindentation-based methods for assessing mechanical properties of brittle oxide ceramics, facilitating material discovery and optimization for thermal barrier coatings and other high-temperature applications.
1. Introduction
Thermal barrier coatings (TBCs) are critical for protecting superalloy components in high-temperature environments, yet conventional yttria-stabilized zirconia (YSZ) suffers from high thermal conductivity and phase instability above 1473 K. Emerging candidates like A2B2O7-type oxides (e.g., RE2Zr2O7) offer low thermal conductivity but exhibit inadequate fracture toughness (KC ~1.0–1.5 MPa·m1/2), limiting their service life. The bottleneck lies in balancing thermal insulation with mechanical robustness—specifically, achieving high hardness and fracture toughness while maintaining low elastic modulus to accommodate thermal expansion mismatches.
This study addresses this gap by systematically evaluating RE3TaO7 (RE=La, Sm, Eu, Gd, Dy, Lu) weberite-type ceramics, which have shown promising thermal properties (thermal conductivity 1.0–1.5 W·m−1·K−1, TECs 9.7–10.8×10−6 K−1 at 1773 K). Using nanoindentation, the authors quantify H, E, KC, and wear resistance, and critically assess the validity of various KC calculation methods for brittle oxides. By identifying the appropriate equations based on crack geometry (l/α ratio), they provide a reliable framework for mechanical characterization, directly supporting the development of next-generation TBCs with superior durability.
Loading authentic research manuscript (Pages 1–5)...
Chenyu Li, Lin Chen, Guiyu Xue, Jiankun Wang, Baihui Li, Xiang Jiang, Jing Feng (2026). Comprehensive Mechanical Properties of Oxide Ceramics Measured by Nanoindentation: RE3TaO7 (RE=La, Sm, Eu, Gd, Dy, Lu) as a Study Case. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3779-1
Research & Educational Purpose Only: The translations, structured abstracts, analytical annotations, and data reports provided by SinoGreenTechare intended exclusively for academic research, internal corporate R&D, and educational benchmarking. They do not constitute formal engineering, chemical safety, legal, or professional advice.
Copyright & Intellectual Property Notice: Original copyright of the underlying source articles and experimental data remains with the respective authors, institutions, and original publishing journals. SinoGreenTech claims intellectual property only over its proprietary translations, analytical syntheses, and AEO structured enhancements in accordance with international fair use and academic citation principles.
Frequently Asked Questions
What is the optimal method to calculate fracture toughness (KC) from nanoindentation data for brittle oxide ceramics, and how does crack geometry influence the choice?
The choice depends on the ratio of crack length to indentation half-diagonal (l/α). For l/α < 1, Eq. (3) is recommended; for l/α > 1, Eq. (4) is suitable. The indentation energy method is invalid because cracks form at high loads, leading to energy dissipation not accounted for in that model. This ensures accurate KC values, as demonstrated for RE3TaO7 with KC ranging 1.0–2.0 MPa·m1/2.
How do the mechanical properties of RE3TaO7 compare to conventional TBC materials like YSZ and RE2Zr2O7, and what are the implications for high-temperature applications?
RE3TaO7 exhibits H of 5.8–14.9 GPa and E of 127.5–247.8 GPa, comparable to YSZ (H~10 GPa, E~220 GPa). Its KC (1.0–2.0 MPa·m1/2) is higher than RE2Zr2O7 (1.0–1.5 MPa·m1/2) but lower than YSZ (3.5 MPa·m1/2). However, RE3TaO7 offers superior thermal insulation and phase stability, making it a viable candidate for next-generation TBCs where lower thermal conductivity is prioritized.
What is the significance of the wear resistance parameter MDP, and how does it correlate with the microstructure of RE3TaO7?
MDP (0.55–0.67) indicates better wear resistance compared to RE2Zr2O7. This is attributed to the weberite structure, which promotes crack deflection and tortuous crack propagation, increasing energy dissipation during wear. The strong covalent Ta–O bonds and lattice strain fields further resist crack propagation, enhancing durability in abrasive environments.
Can the nanoindentation methods validated in this study be applied to other brittle oxide ceramics, and what are the limitations?
Yes, the methods are generalizable to brittle oxide ceramics, provided the l/α ratio is considered. However, the indentation energy method is not applicable when cracking occurs. The study emphasizes the need for careful crack measurement and selection of appropriate equations to avoid underestimation or overestimation of KC. This framework can accelerate mechanical property screening for new TBC materials.
What are the potential industrial implications of using RE3TaO7 as a TBC material, particularly regarding cost and scalability?
RE3TaO7 offers improved fracture toughness and wear resistance over RE2Zr2O7, potentially extending TBC service life and reducing maintenance costs. However, rare earth tantalates may involve higher raw material costs and complex synthesis. Scalability depends on developing cost-effective fabrication routes, such as atmospheric plasma spraying, which is already used for YSZ. Further research is needed to optimize processing parameters for industrial adoption.
Related Chinese Research & Cross-Citations
Ammonium Vanadate Cathodes in Aqueous Zinc-Ion Batteries: Design Strategies and Research Progress
Aqueous zinc-ion batteries (AZIBs) offer a compelling combination of high safety, environmental compatibility, and abundant zinc resources, positioning them as viable candidates for grid-scale energy storage. Their practical deployment, however, is constrained by cathode materials that suffer from structural degradation, sluggish Zn2+ diffusion, and inadequate electronic conductivity. Ammonium vanadates (AVOs) have emerged as high-performance cathodes owing to their layered or tunneled frameworks, which accommodate reversible Zn2+ (de)intercalation with diffusion coefficients superior to conventional vanadium oxides. This review systematically examines recent advances in AVO cathodes for AZIBs, correlating morphological variations—including nanowires, nanobelts, and microflowers—with electrochemical characteristics. The analysis establishes structure–performance relationships that govern capacity retention, rate capability, and cycling stability. Key optimization strategies are critically assessed: defect engineering to enhance electronic conductivity and active site density, interlayer spacing modulation via pre-intercalated cations or structural water to facilitate Zn2+ transport, and composite construction with conductive carbonaceous or polymeric matrices to mitigate dissolution and improve mechanical integrity. Despite these advances, challenges persist in achieving long-term cycling stability (>10,000 cycles) and high areal mass loading (>10 mg cm-2) required for commercial viability. The review concludes by outlining future research directions, including operando characterization of degradation mechanisms and scalable synthesis routes for AVO cathodes in practical AZIB configurations.
Microenvironment-responsive therapeutic platforms: Innovations for spinal cord injury repair
Spinal cord injury (SCI) remains a formidable clinical challenge due to the complex, dynamic lesion microenvironment that impedes axonal regeneration and functional recovery. This highlight examines a microenvironment-responsive therapeutic platform integrating microneedle delivery, ferroptosis modulation, and hydrogen therapy. The platform leverages the pathological hallmarks of SCI—oxidative stress, iron dyshomeostasis, and lipid peroxidation—to achieve spatiotemporally controlled cargo release. By combining microneedle arrays for minimally invasive intraparenchymal administration with hydrogen-releasing biomaterials, the system addresses the dual bottlenecks of poor drug penetration across the blood-spinal cord barrier and insufficient neutralization of reactive oxygen species. Ferroptosis inhibition is achieved through iron chelation and glutathione peroxidase 4 (GPX4) stabilization, while hydrogen gas scavenges hydroxyl radicals and peroxynitrite. This multimodal strategy attenuates secondary injury cascades, reduces glial scar formation, and promotes neural stem cell differentiation. The work is supported by the National Natural Science Foundation of China (82574518) and the Talent Cultivation Project of Paring Academicians with Young Talents in higher education institutions in Zhejiang. The authors declare no conflict of interest. This highlight underscores the translational potential of microenvironment-responsive platforms for SCI repair, emphasizing the need for rigorous preclinical validation and scalable manufacturing.
Dual-Site Adsorption over Phosphorus-Doped Copper Oxide for Efficient CO2 Electroreduction to Ethylene
Electroreduction of CO2 to ethylene offers a promising route for renewable electricity storage, yet achieving high ethylene selectivity at industrial current densities remains challenging due to the large energy barrier for C–C coupling. Here, we report a “MOF-assisted in situ doping” strategy to introduce the oxophilic nonmetal phosphorus (P) into the copper oxide (CuO) lattice, constructing a localized Cu–P dual-site adsorption configuration for the key *OCCHO intermediate. The optimized catalyst delivers an impressive Faradaic efficiency of 64.6% for ethylene with a partial current density of 646 mA cm-2. Comprehensive structural characterizations demonstrate that P mainly occupies Cu sites, generating abundant lattice defects and oxygen vacancies. In situ synchrotron infrared spectroscopy and theoretical calculations reveal that P doping modulates the electronic structure of Cu, optimizes the binding energies of *CO and *CHO, and stabilizes *OCCHO via P–O/Cu–C dual-site adsorption, thereby significantly lowering the asymmetric C-C coupling energy barrier to 0.74 eV. This work highlights a dual-site microenvironment regulation strategy for CO2-to-ethylene electroreduction.
Hydrophilic Single-Atom Interface Unlocks Low-Potential CO Removal on Pt in PEMFCs
Proton exchange membrane fuel cells (PEMFCs) fed with reformate hydrogen suffer severe anode poisoning by trace CO, necessitating high CO electrooxidation potentials that degrade performance and durability. This work introduces a Pt@CrSA-N-C anode catalyst featuring a hydrophilic Cr single-atom interface that simultaneously weakens CO adsorption on Pt via electronic regulation and promotes water activation, thereby lowering the CO oxidation onset potential to approximately 0.13 V vs. RHE. The onset potential was determined by two independent methods: the first potential at which the background-corrected current exceeds 0 mA cm-2 during CO oxidation reaction tests in a three-electrode system, and the potential at which the forward scan current exceeds the N2 background current in CO-stripping voltammetry. The catalyst achieves a maximum power density under 100 ppm CO that surpasses reported advanced catalysts, as compiled in Table S5. Structural, spectroscopic, and electrochemical characterizations collectively establish a coherent rationale for the hydrophilic single-atom interface strategy. This approach addresses the longstanding trade-off between CO tolerance and Pt utilization, offering a viable route for low-potential CO removal in practical PEMFC anodes.
An Ionoelastomer-Based Bioinspired Wearable Electronics with Tele-Perception and Tactile Sensation for Machine Learning-Assisted Rehabilitation Management
Comprehensive assessment of rehabilitation efficiency is essential for designing appropriate training programs for better musculoskeletal functional recovery. Existing contact-receptor-dependent rehabilitation assessment systems mostly focus on assessing the restoration of muscle function by evaluating grip strength or joint flexion angle; however, parameters reflecting neuromuscular synergistic function are always overlooked. Herein, we develop an ionoelastomer-based soft artificial electroreceptor (SAER) that integrates tele-perception and tactile sensation to track the rehabilitation process, collecting signals related to approaching speed and grip strength sequentially. The SAER uses polyurethane ionoelastomer incorporated with quasi-solid conductive salt as the electric field receptor, and is integrated on a rehabilitation-training ball after assembly to establish an untethered detection device; this enables the remote capture of hand approaching parameter within a 9 cm range, followed by the quantification of grip strength when contacting and grasping. Furthermore, a data-driven assessment system is established by integrating machine learning, which accurately classifies rehabilitation efficiency into six levels; it supports for rehabilitation evaluation and training programs adjustment. Overall, the SAER-based rehabilitation management system establishes a paradigm that synergistically evaluating parameters corresponding to neuromuscular functional restoration and holds strong potential for home-based active rehabilitation for minimizing dependence on frequent clinical supervision.
Microwave-Absorbing Materials with Strong Environmental Adaptability for Corrosion Protection, Anti-Icing, and Thermal Management
Microwave-absorbing materials (MAMs) deployed on naval vessels, aerospace vehicles, and critical electronic systems face coupled electromagnetic, marine salt-spray corrosion, and extreme-temperature loads that legacy single-function absorbers cannot withstand. This review consolidates progress on three environmentally adaptive MAM classes: corrosion-protective, anti-icing, and thermal-management absorbers. The electromagnetic loss and impedance-matching fundamentals are first established, then the synergistic mechanisms, design strategies, and characterization protocols for each class are examined against representative material systems and their measured performance. The analysis identifies a shared design logic—multiscale hierarchical architecture, interfacial polarization engineering, and multifunctional phase integration—while distinguishing the divergent protection mechanisms: barrier and passivation effects for corrosion, surface-energy and latent-heat regulation for anti-icing, and phonon–electron transport decoupling for thermal management. Persistent bottlenecks include the trade-off between impedance matching and protective-layer density, the absence of standardized coupled-field test protocols, and the scarcity of long-term salt-spray and thermal-cycling durability data. Future directions are delineated: intelligent self-adaptive absorbers, multiphysics-coupled simulation frameworks, and environmentally benign multifunctional integration. The review provides a theoretical and technical basis for the design, construction, and engineering scale-up of next-generation high-performance absorbers for aerospace, electronic, and marine equipment.