Developing transparent shielding materials combining gamma-ray/neutron radiation attenuation with extreme-environment stability remains challenging due to a limited understanding of "composition-structure-property-stability" relationships. Here, an innovative design strategy was proposed to fabricate rare-earth RE2Zr2O7 (RE = La, Gd, Y, Yb) transparent ceramics with > 75% optical transmittance, elucidating the micro-mechanisms governing their radiation hardness. By decreasing the rare-earth cation radius drives a lattice transition from an pyrochlore to a defect fluorite structure, it identified that while pyrochlore La- with high optical quality exhibits intrinsic resistance to 100 kGy gamma-irradiation, defect-fluorite Y- with wide transparency and Gd- with extremely neutron shielding suffer from defect-induced darkening. Crucially, an radiation-hardening mechanism in disordered Yb- with high-density is uncovered, where intrinsic Yb2 + /Yb3+ redox couples act as robust charge buffers to neutralize radiation-induced charges. Combined with tunable shielding capacities of RE2Zr2O7, this work provides a foundational framework for designing next-generation, multifunctional shielding windows tailored for complex mixed-radiation fields.

Introducing a high density of grain boundaries into ceramic waste forms has been shown to significantly enhance their irradiation resistance. However, this strategy is likely to compromise their leaching resistance. To date, this view still lacks experimental verification. Furthermore, the corrosion behavior and nuclide leaching mechanisms of nanocrystalline ceramic waste forms remain unclear. Herein, xTRPO-(1-x)Gd2Zr2O7 (x = 0.3 and 0.5) ceramics with grain sizes ranging from the nanoscale (53.6 nm) to the micron scale (13.4 & micro;m) were synthesized, and their chemical durability was investigated via semi-dynamic leaching tests. The normalized leaching rates (LRi) for both micron- and nanog-rained ceramics fell within the range of 10(-5)similar to 10(-6) g.m(-2)& centerdot;d(-1) after 42 days, indicating good chemical durability, although the nano-grained ceramics exhibited slightly higher release rates. We demonstrate distinct surface alteration behaviors for the first time: an amorphous film formed on the micron-grained samples, whereas a crystalline, multilayered structure developed on the nano-grained samples after leaching. Both alteration layers can act as protective barriers against aqueous corrosion, contributing to reduced long-term release rates. These findings provide valuable insights into performance prediction and material design for next-generation ceramic waste forms.

This study pioneers the application of a gadolinium zirconate (Gd2Zr2O7)-based matrix for immobilizing simulated cesium (Cs) nuclides in high-level radioactive waste (HLW) owing to its superior nuclear waste loading capacity and radiation resistance. And a low-temperature procedure composed of the glycine-nitrate combustion, the cold sintering process (CSP) and subsequent annealing treatment is developed in this work. First, a Cs-Ce co-doping route is adopted which successfully increases Cs solubility in the Gd2Zr2O7 lattice from 7.5 mol% to 12.5 mol%. Gd1.25Ce0.5Cs0.25Zr2O7 nanocrystalline powders (∼10 nm) are obtained after calcined at 600°C. Subsequently, initial densification by CSP at 300°C yields ceramics with a density of 5.89 g/cm3. By further annealing at 600°C, the density of the ceramic is enhanced to 6.26 g/cm3. The maximum treatment temperature is limited to 600°C throughout the process, and the final immobilization amount is estimated to be 10.51 mol% in a 90% T.D. ceramic. In addition, the 42-day normalized Cs leaching rate of the optimized ceramic reaches 8.1792 × 10−3 g m−2 d−1, which is comparable to that of classic Synroc-C waste forms, verifying its basic feasibility for high-level radioactive waste immobilization. These findings demonstrate that Gd2Zr2O7 exhibits potential as an immobilization matrix for Cs, while the developed low-temperature synthesis route shows promise for fabricating ceramics incorporating volatile elements.

While spherical powders are typically favored for enhanced sintering activity, highly transparent Y 2 O 3 –MgO ceramics have recently been fabricated using rod-like powders. The underlying mechanisms by which powder morphology influences the final microstructure and properties remain unclear. This study reveals that spherical powders yield spherical-phase domains and high mid-wave infrared transmittance (~84% at 3 μm). In contrast, rod-like powders promote elongated phase domains and a higher long-wave infrared transmittance (~82% at 8 μm) with a broader transmission window. Both composites exceed 85% (~6 μm) transmittance (theoretical maximum ~86%). Optical tailoring is attributed to the interplay of Mie scattering, carbon contamination, intrinsic phonon absorption mechanisms, and pinning effect. Composites from rod-like powders also exhibit finer grains and higher hardness (11.3 GPa vs. 10.2 GPa), consistent with the Hall–Petch relationship. This work demonstrates that powder morphology design enables concurrent optimization of performance in transparent materials, offering a general strategy for advanced ceramic engineering.

Transparent spinel-type aluminum oxynitride(γ-AlON)ceramics have emerged as a highly promising material for military protection(e.g.,infrared windows,armor materials)and civilian optics(e.g.,lenses,semiconductor devices)due to their excellent optical properties(high transmittance,broad transmission band),outstanding chemical stability,and superior mechanical strength.Transparent ceramics require not only high optical transmittance but also high mechanical properties,which is the fundamental prerequisites for the practical application of AlON ceramics.The incorporation of sintering aids is a critical strategy in fabricating transparent AlON ceramics,as optimizing their type and content allows precise control over microstructural evolution during sintering,including grain nucleation and growth,phase distribution,and overall densification.Consequently,these microstructural modifications directly influence the ceramic's properties,such as,optical transmittance,mechanical strength,and chemical stability,enabling their effective regulation and optimization for advanced applications.This paper comprehensively reviews the research progress on sintering aids for preparing high-quality AlON transparent ceramics.The sintering aids are categorized into rare earth oxides(Y2O3,La2O3,and Pr2O3),alkaline earth oxides(CaCO3and MgO),and silicon-based compounds(SiO2 and Si3N4).The review delves into the effects of these aids on the optical and mechanical properties of AlON transparent ceramics and details their mechanisms in promoting densification,optimizing grain size distribution,suppressing phase decomposition,and lowering sintering temperature.Optimal sintering aids facilitate pore elimination and suppress abnormal grain growth via liquid-phase formation or pinning effects,thereby enhancing optical transmittance while simultaneously improving mechanical properties(hardness,fracture toughness,and strength)through microstructural refinement.The mechanisms of sintering aids in AlON densification vary significantly depending on their chemical nature.Specifically,rare-earth additives predominantly facilitate liquid-phase sintering,alkali metals induce grain-boundary pinning effects,while silicon-based compounds primarily form solid solutions.This review also analyzes the existing problems and challenges in current research and looks forward to future research directions,aiming to provide theoretical guidance and technical reference for the preparation of high-performance AlON transparent ceramics.

Fine-grained biphasic Li2.1TiO3 tritium breeder ceramics were fabricated within 10 min via ultra-fast high-temperature sintering (UHS). Optimized sintering at 45 V and 500 Hz for 10 min yielded ceramics with a high relative density of 93.89% and an average grain size of 0.92 & micro;m. This resulted in excellent mechanical properties (compressive strength: 110 +/- 5 MPa, flexural strength: 67 +/- 3 MPa) and a room-temperature thermal conductivity of 3.65 W/m & sdot;K. Microstructural analysis revealed a submicron-scale coexistence of monoclinic beta and cubic gamma phases. The ceramics exhibited significantly enhanced ionic transport, with an ionic conductivity of 7.9 & times; 10-4 S/m and an effective Li+ diffusion coefficient of 9.1 & times; 10-11 m2/s. Grain-growth kinetics indicated a voltage-dependent mass-transport regime driven by multiple synergistic factors at the optimum condition. This study demonstrates UHS as a rapid and effective technique for producing high-performance Li2.1TiO3 ceramics, offering a promising fabrication route for advanced tritium breeder materials.

Transparent cubic alumina (gamma-Al2O3) ceramics are promising optical materials but are challenging to densify without phase transformation or cracking. Herein, we report a novel H2O-assisted high-pressure sintering (HPS) strategy that enables the fabrication of highly transparent, crack-free gamma-Al2O3 ceramics at temperatures as low as 300 degrees C. By combining GPa-level pressures (0.8-5 GPa) with precisely controlled H2O concentrations (5-75 wt%) as a transient solvent, we achieve near-theoretical densities (> 99%) and exceptional optical transmittance (> 80% in the visible range). Systematic investigation reveals a non-monotonic dependence of densification and transparency on H2O content, with an optimal concentration of similar to 15 wt% under 5 GPa. Microstructural and spectroscopic analyses correlate superior optical quality with a pore-free, nanocrystalline microstructure and the absence of secondary phases. Crucially, through integrated first-principles calculations and ab initio molecular dynamics simulations, we unravel the atomic-scale mechanism. Namely, under high pressure, H2O dissociates at the particle interface, with the resultant H+ forming Al-H bonds and OH- incorporating into interstitial lattice sites. This process stabilizes a hydroxyl-cubic aluminate (HAl2O4)-like structure, which not only facilitates stress-free densification via an enhanced dissolution-precipitation pathway but also effectively relieves internal stresses that typically cause cracking in pressure-only sintering. This work provides a fundamental mechanistic understanding of the synergistic role of H2O and ultra-high pressure in low-temperature ceramic consolidation, establishing a generalizable route to transparent nanocrystalline ceramics that are otherwise inaccessible via conventional thermal sintering.

High-pressureless sintering temperatures in the industrial fabrication of transparent AlON ceramics result in elevated production costs, highlighting the need to develop novel strategies to lower the sintering temperature. In this study, the AlON ceramics with high transmittance of similar to 81% were successfully sintered at a lower temperature of 1800 degrees C by co-doping with BaO-SiO2 as novel sintering additives. The effects of BaO-SiO2 on the phase composition, microstructure, and optical properties of AlON ceramics were systematically investigated, and the underlying mechanism by which the BaO-SiO2 co-doping promotes pressureless sintering was elucidated. This work provides a cost-effective and energy-efficient approach for producing highly transparent AlON ceramics.

The development of high-performance shielding windows capable of attenuating both neutron and gamma radiation is critically important for nuclear applications. However, most existing windows are limited by single-ray shielding and severe irradiation coloration. To address this, high-density Lu2Hf2O7 transparent ceramics were developed in this work. The prepared ceramics exhibit high optical quality, with a maximum transmittance of 77.8%, approaching the theoretical limit of 78.8%. Benefiting from the high effective atomic number, efficient gamma-ray attenuation is achieved, characterized by a linear attenuation coefficient of 0.745 cm-1, with a 1-cm-thick sample attenuating more than 50% of gamma rays from a 137Cs source. In addition, Monte Carlo neutron transport simulations indicate effective neutron attenuation, with a 1.8-cm-thick sample reducing the 1 eV neutron flux by over 50%. These results demonstrate that Lu2Hf2O7 transparent ceramics provide a viable combination of optical transparency and gamma-ray/neutron shielding, highlighting their potential for radiation-shielding window.

As a key processing parameter, sintering temperature significantly influences the microstructure evolutions, phase transitions, and resultant physical properties of AlON transparent ceramics. However, the AlON ceramic material, due to its strong covalent bonds and high melting point, requires extremely high sintering temperatures (1880 degrees C-1980 degrees C) to achieve transparency, which results in the challenges of energy consumption, microstructure control, and cost. Thus, developing efficient low-temperature sintering strategies is essential. In this study, we successfully reduced the pressureless sintering temperature by approximately 200 degrees C through the introduction of a novel sintering additive, BaO, achieving transparent ceramics with over 80 % transmittance at a low temperature of 1750 degrees C. This work systematically investigates the effects of BaO on the phase composition, microstructure, and optical properties of AlON, while elucidating the underlying mechanism by which BaO promotes sintering.

Recent developments of rare earth (RE) based control rod materials call for systematic search for optimal compositions with enhanced and sustained neutron absorption capabilities. This study employs the Reactor Monte Carlo (RMC) code to evaluate the control rod worth and the worth loss during burnup of rare earth (RE) (Z = 62-71) titanates (RE2TiO5 and RE2Ti2O7). A simplified model equivalent to the AP1000 full-core burnup environment was established to assess reactivity worth, depletion loss, and burnup stability. Results demonstrate that the RE2TiO5 system outperforms RE2Ti2O7 due to its higher nuclide density, which enhances macroscopic absorption cross-section and slows reactivity loss. Among the rare-earth elements, Eu and Dy exhibit high reactivity worth with low depletion, while Sm and Tb show increasing-worth pattern. Based on the transmutation characteristics, a micro-doping strategy (e.g., 1% Tb doped in Dy2TiO5) is developed. The reactivity worth loss at end of life (EOL) can be reduced by approximately 20% compared to the single-component absorber, which is attributed to the continuous generation of effective progeny nuclides from the dopant to compensate for depletion.

Y2O3-MgO composites have emerged as promising mid-infrared (MIR) materials owing to their exceptional broadband transmittance and remarkable thermal stability at elevated temperatures. Nevertheless, the presence of uncontrollable absorption bands within the 4-7 mu m spectral range, compromises their optical performance in advanced MIR systems. To address this limitation, we systematically investigated annealing as a strategic approach for modulating defect chemistry in oxide composites. In this paper, the absorption peaks of Y2O3-MgO composites were controlled by varying the annealing conditions. As the annealing temperature increases from 600 degrees C to 1100 degrees C, the absorption peaks of Y2O3-MgO composites gradually shift from-4.9 mu m to-6.8 mu m, with a transition temperature-900 degrees C. This behavior is attributed to the oxidation of metal-organic coordination (MOC) to CO32-in high-temperature air. Ultimately, Y2O3-MgO composites featuring controllable absorption peaks were obtained, demonstrating a transmittance of-81 % at 7 mu m-the highest value ever reported for this composite system, which broadens the potential application space, particularly in fields requiring mid-infrared transparency such as gas detection, materials characterization, and biomedical imaging. This study not only elucidates specific strategies for enhancing the performance and microstructure of Y2O3-MgO composites but also furnishes reliable methodologies and datasets to support the annealing processes of other material systems.

ABSTRACT Ultraviolet B emission around 311–313 nm (NB‐UVB) materials are crucial for medical phototherapy and disinfection. Currently, most existing NB‐UVB materials are phosphors, which often suffer from insufficient chemical, thermal, and optical stability under extreme conditions. Motivated by the superior physicochemical stability of transparent ceramics compared to their powder counterparts, in this work, we developed a novel Gd 3+ ‐doped Lu 2 O 3 transparent ceramic for NB‐UVB materials. The prepared ceramic samples exhibit excellent optical transparency, with an in‐line transmittance of approximately 80% at 800 nm. Microstructural analysis shows that with increasing Gd 3+ content, the ceramic exhibits a uniform microstructure, with the average grain size increasing from 16.85 µm to 40.04 µm. Furthermore, after Gd 3+ doping, internal f–f transitions were observed at 276 nm and 315 nm, with a fluorescence lifetime in the millisecond range. This work provides a viable strategy for developing robust NB‐UVB‐emitting transparent ceramic materials.

Magnesium aluminate spinel (MgAl2O4) is a technologically important transparent ceramic with a broad optical window, high hardness, excellent thermal stability, and good chemical durability, making it attractive for infrared windows, transparent armor, and related optoelectronic components. However, pressureless densification of spinel remains difficult because the diffusion of Mg2+ and Al3+ ions is intrinsically sluggish, so conventional sintering typically requires long dwell times or pressure-assisted routes such as hot pressing and hot isostatic pressing. In this work, pressureless ultrafast high-temperature sintering (UHS) was employed to densify MgAl2O4 spinel ceramics. Starting from a green compact with an initial relative density of about 55%, the samples were rapidly heated to 1750 u2103 at rates exceeding 1000 u2103u00B7min-1, held for only 5 s, and then cooled in vacuum. The sintered body retained a single cubic spinel phase, with no detectable secondary phases in XRD. Archimedes measurements gave a relative density of 98.2%, corresponding to a low residual porosity of 1.8%. The microstructure consisted of fine equiaxed grains with an average size of 0.62 u00B1 0.13 u03BCm, together with a small amount of residual pores located mainly at grain boundaries and triple junctions. After polishing to a thickness of about 1 mm, the specimen exhibited an in-line transmittance of 64.7% at 5.3 u03BCm and showed a monotonic increase in transmittance with wavelength, consistent with residual pore scattering in the mid-infrared region. The enhanced densification achieved by UHS is attributed to two coupled effects. First, the extremely fast heating schedule suppresses the low-temperature stage dominated by surface diffusion, thereby limiting unnecessary grain coarsening and preserving a high sintering driving force at the peak temperature. This fine-grain retention is critical because the densification rate in grain-boundary-diffusion-controlled sintering depends strongly on grain size. Second, the severe thermal shock associated with UHS may freeze grain boundaries into high-energy, non-equilibrium states, which could accelerate grain-boundary diffusion and facilitate pore elimination, although this mechanism is presently supported only by indirect evidence and requires direct atomic-scale verification in future work. For comparison, a conventional pressureless sintering schedule of 10 u2103u00B7min-1 to the same peak temperature followed by a 5 s hold produced a much lower relative density of 74.2% and a coarser grain size of about 2.31 u03BCm. These results demonstrate that UHS provides a powerful pressureless route for rapidly densifying diffusion-limited spinel ceramics and offers a viable basis for the preparation of small-sized transparent MgAl2O4 components.

Transparent ceramics are critical for advanced optics and armor, but shaping them into highly curved geometries without degrading their optical and mechanical properties remains a formidable challenge. Here, we introduce a force-driven sintering strategy that harnesses force-induced creep to dynamically control microstructure and curvature through continuous stress release. A hallmark of this process is a dynamic curvature reversal phenomenon, governed by cyclic stress accumulation and release. Using force-driven sintering, we fabricated large-scale (0.5*2*22 cm3) curved MgAl2O4 ceramics exhibiting a high curvature (>5.36 m-1), and exceptional transmittance exceeding 85% (approaching the theoretical limit), while matching the best-reported mechanical properties. We also demonstrate the versatility of force-driven sintering by producing curved Al2O3 transparent ceramics. This method synchronizes external mechanical forces with intrinsic material creep and stress relaxation, enabling the single-step fabrication of complex-shaped, high-performance transparent components. force-driven sintering establishes a scalable and versatile manufacturing paradigm for transparent ceramics in demanding applications.

Highly transparent polycrystalline gadolinium zirconate (Gd2Zr2O7, GZO) ceramics are excellent candidates for mixed gamma (gamma) and neutron radiation shielding, but suffer from gamma-induced color centers. To address this, we introduce a Ce-doping-mediated defect-engineering strategy, demonstrating that the Ce valence state is the critical switch. We show that Ce4+-rich (air-annealed) samples exhibit exceptional radiation-hardening, whereas Ce3+-rich (vacuum-sintered) samples show catastrophic sensitization. It is confirmed that Ce4+ acts as a preferential electron trap, competitively suppressing color center formation. As a result, the optimized Ce4+-rich samples exhibit a gamma-induced transmittance loss of less than 4 % (at 100 kGy) and maintain excellent transparency (71.8 % at 450 nm), vastly outperforming commercial ZF6 lead glass (which suffers a 52.6 % loss). Furthermore, GZO:Ce demonstrates 20 % higher gamma attenuation (0.373 cm(-1) for Co-60) and exceptional thermal neutron shielding (cross-section of 688.22 cm(-1)), combined with excellent mechanical hardness (similar to 11.5 GPa) and superior corrosion resistance in both acidic and alkaline media. This work establishes Ce-doped GZO as a scalable and durable ceramic platform for gamma/n shielding windows, and highlights valence-state and defect engineering as a powerful strategy for the rational design of radiation-tolerant transparent materials.

Biphasic lithium-based ceramics have been identified as a potentially valuable material for solid-state tritium breeders, yet significant challenges persist in optimizing their comprehensive performance and enhancing thermal cycling stability. In this study, mechanical alloying was employed to introduce a high density of oxygen vacancies into Li2TiO3 and Li4SiO4 powders, yielding biphasic ceramics that exhibit favorable overall performance and thermal cycling stability. The microstructure and properties of the biphasic ceramics were systematically investigated, with a focus on the influence of phase ratio of two phases on thermal conductivity, ionic conductivity, and thermal cycling stability. The results show that the 3Li2TiO3/Li4SiO4 composite exhibits superior comprehensive performance, including a room-temperature thermal conductivity of 2.86 W/m & sdot;K, an ionic conductivity of 3.42 & times; 10-5 S/m, and excellent thermal cycling stability. This remarkable stability is attributed to the dense microstructure and fine grain size of the sintered ceramics promoted by oxygen vacancies, as well as the grain-boundary pinning effect of Li2TiO3 during the thermal cycling process.

Oxygen defect tuning engineering is an effective method to tailor the properties of ceramic materials. However, persistent difficulties remain in the controllable generation of intrinsic oxygen vacancy defects () in the AlON lattice, and their influence on transparency remains elusive. Here, by regulating the CRN synthesis temperature to implant thermal‐induced intrinsic defects into AlON powder, we report that higher temperature would cause the lattice oxygen to be lost from the AlON crystal, and result in the AlON powder exhibiting a distinct gray color. Besides, through an analysis of the sintering kinetics in ceramics fabrication, AlON ceramics prepared from powder with more defects show a high transmittance up to 82%, while the counterpart ceramic only achieves a transmittance of 76%. The study of intrinsic defects on ceramics transparency in this work provides a reference approach for fabricating AlON transparent ceramic.

The advancement of Li4SiO4 ceramics with enhanced performance represents a crucial research area within the domain of solid-state tritium breeding materials. However, the mechanical and physical properties of Li4SiO4 are severely constrained by the challenge of balancing between densification and grain refinement. In this study, a ceramic with a high density and a distinctive cauliflower-like nanostructure is proposed. Specifically, Li4SiO4 nanopowders with varying oxygen vacancy contents were obtained via the mechanical alloying process. The issues of low diffusivity and abnormal grain growth during the sintering of Li4SiO4 ceramics were effectively addressed through the nonstoichiometrically activated sintering method. The resulting Li4SiO4 ceramics exhibited a high relative density (90.21 % T.D.), exceptional mechanical strength (104 N), high thermal conductivity (2.98 W/m center dot K at room temperature and 1.91 W/m center dot K at 500 degrees C), and good ionic conductivity (4.20 x 10-4 S/m). The findings indicated that the oxygen vacancies in Li4SiO4 powders increased with the prolongation of the mechanical alloying period. This increase contributed to enhanced relative density, crushing load, and thermal conductivity of Li4SiO4 ceramics, with only a slight decline in ionic conductivity. Concurrently, the oxygen vacancies in the ceramics were almost entirely annihilated by sintering under an air atmosphere. In conclusion, the utilization of nonstoichiometrically activated sintering offers significant advantages in the fabrication of tritium breeding ceramics with superior comprehensive characteristics.