Journal of the American Ceramic Society最新文献

Most ceramics have low fracture toughness (<5 MPa $�\sqrt{�m�}$) at room temperature. This work explores the feasibility of toughening TiO₂ via femtosecond laser shock peening (fs-LSP). Transmission electron microscopy (TEM) analyses reveal LSP-induced the creation of high-density stacking faults, dislocation structures, and twin boundaries in the LSP-treated surface layer (∼55 µm thick) of single-crystal rutile TiO₂. Meanwhile, oxygen vacancies were introduced into TiO₂ via the LSP treatment, as evidenced by X-ray photoelectron spectroscopy (XPS) results and the red peak shifts in Raman spectra. In addition, X-ray diffraction scans show in-plane compressive residual stress (−61 to −306 MPa) built in LSP-processed TiO_2. The indentation fracture resistance (K_IFR) of TiO₂ is enhanced from 2.8 $��\mathrm{MPa}�\sqrt{�m�}�$ to 6.8–8.2 $��\mathrm{MPa}�\sqrt{�m�}�$. The role of compressive residual stress, oxygen vacancy, dislocations, stacking faults, and twins are discussed using atomistic simulations, semiquantitative and qualitative analyses. This study demonstrates the remarkable synergistic effects of defect networks and residual compressive stress in toughening TiO₂ and possibly other ceramic materials. Our work also qualifies the fs-LSP as an effective and scalable method to toughen ceramic materials.

Alloying is a widely used strategy for reducing lattice thermal conductivity through phonon scattering induced by mass and strain fluctuations. However, the evaluation of disorder-scattering parameters in multi-sublattice compounds remains inconsistent because both atomic- and unit-cell-based formulations are used in the literature. In this work, the origin of these discrepancies is systematically examined using ZrC and ZrB₂ as model systems. We show that the two approaches yield equivalent predictions only when a consistent basis is maintained throughout the calculation and the alloyed site has a degeneracy of unity. For compounds containing multiple sublattices or higher site degeneracy, the formulations diverge and can lead to substantially different estimates of alloying-induced phonon scattering. To address this issue, a generalized framework incorporating sublattice-selective disorder scattering is proposed. The formulation preserves basis consistency while accounting for the localized nature of disorder in complex compounds. The model is applied to W-doped ZrB₂ ceramics and compared with experimental thermal conductivity measurements. Improved agreement is obtained relative to conventional treatments. The proposed framework provides a physically consistent methodology for evaluating point-defect scattering in multi-sublattice solid solutions and enables more reliable prediction of lattice thermal conductivity in complex ceramic materials.

Oxyfluorides containing up to 75 wt% of recycled glass from end-of-life solar panels have been investigated. Reduced processing temperature and high transparency have shown that the material has potential for optical applications. In this work, cerium-doped samples were investigated. Spectroscopic study reveals the presence of $�{\mathrm{Ce}}^{�3�+�}$, and luminescence from these ions and oxygen-deficient centers was detected. Raman demonstrated that cerium affects the glass network by promoting polymerization. In turn, thermal analysis indicated some changes in the crystallization events between 500$��{}^{\circ }�C�$ and 800$��{}^{\circ }�C�$, which were confirmed by in situ X-ray powder diffraction measurements. Crystallization of fluorite, xonotlite, and combeite was confirmed, while other phases give minor contributions to the XRD patterns. Cerium addition reduced the formation of xonotlite, mainly above 700$��{}^{\circ }�C�$. The potential applications of the material and the further studies required are discussed.

Fully crystalline, dense environmental barrier coatings (EBCs) are required to protect SiC-based ceramic matrix composites, which are the advanced structural materials for hot-section components of gas turbines. Thermal spray technologies, which have been widely used for depositing thermal barrier coatings, are also applied to deposit EBCs. Avoiding the segmental cracks is one of the main challenges in depositing thermal sprayed EBCs. In this work, suspension plasma spraying (SPS) was used to deposit EBCs on the SiC substrates. The combustion of an ethanol-based suspension can bring plasma additional enthalpy. As a result of that, extremely high deposition temperatures (above 1200°C) could be achieved. At such high deposition temperatures, fully crystalline crack-free Yb₂Si₂O₇ coatings were successfully obtained. However, A relatively high amount of Yb₂SiO₅ phase was observed in the as-sprayed coatings. The high amount of the Yb₂SiO₅ phase was attributed to the high surface ratio of the particles formed during the suspension plasma spray.

Magnesium oxide (MgO) serves as a model material for plastically deformable ceramics. In previous studies, it has mainly been investigated via uniaxial compression, with studies often focusing on a particular deformation mechanism and temperature range. In this work, the novel high temperature scanning indentation (HTSI) nanoindentation method is applied to characterize the mechanical properties of single-crystalline MgO from room temperature to 800°C, allowing a quasi-continuous measurement of hardness, elastic modulus, the coefficient of strain rate sensitivity, and the activation volume.

Results show that the hardness is controlled by hard 1/2<110>{100} slip, while the activation parameters are influenced by both 1/2<110>{100} and 1/2<110>{110} slip systems. The temperature dependence of the hardness follows two linear regimes, while the strain rate sensitivity shows complex behavior with a maximum of m = 0.05 at a temperature of 675°C. In the same regime, the activation volume remains approximately constant at V = 10–20 b³. At higher temperatures, it increases to V = 100 b³. The combined hardness and activation parameter data enable the determination of transition temperatures between different deformation regimes. With increasing temperature, MgO first shifts from a kink-pair to an obstacle-controlled regime at 240°C, with long-range dislocation interactions setting in at higher temperatures above 675°C.