Cover Image, Volume 102, Issue 11doi: 10.1111/jace.15851pmid: N/A
Cover Photograph: Conceptual representation of the confl uence of data science and informatics with ceramic and glass science. Circular images from left: MAX phases (courtesy M. Radovic), fi ber optics, injection molded ceramic parts (courtesy Ceramco Inc.), a glass manufacturing process. Credit: Tess Speakman (The American Ceramic Society). DOI: 10.1111/jace.16677
Er3+ cross‐section spectra of Er3+/Pr3+:Gd3Ga5O12 single‐crystal: Pr3+‐codoping effectXu, Qing; Wang, Yan; Chen, Feng; Wong, Wing‐Han; Zhang, Zi‐Bo; Zhang, De‐Long
doi: 10.1111/jace.16554pmid: N/A
Fluorescence and absorption spectra at 530 nm (2H11/2→4I15/2), 560 nm (4S3/2→4I15/2), 660 nm (4F9/2→4I15/2), 980 nm (4I11/2→4I15/2), 1530 nm (4I13/2→4I15/2), and 2710 nm (4I11/2→4I13/2) of Er3+ in Gd3Ga5O12 single‐crystal codoped with Pr3+ have been measured. Judd‐Ofelt analysis yields the intensity parameters Ω2 = (0.68 ± 0.03) × 10−20 cm2, Ω4 = (0.60 ± 0.07) × 10−20 cm2, and Ω6 = (0.90 ± 0.17) × 10−20 cm2. A comparison with previously reported values of Er3+‐only doping case shows that Pr3+‐codoping causes slight change of both Ω2 and Ω4, while onefold increase of Ω6. From calculated radiative rates and measured fluorescence spectra, Er3+ emission cross‐section spectra were calibrated at first. Then, the absorption cross‐section spectra were calculated using McCumber relation. In parallel, the absorption cross‐section spectra were also obtained from the measured absorption spectrum, and compared with those obtained from the McCumber relation. The comparison shows that both methods give consistent result of absorption cross‐section spectrum. Further comparison with Er3+‐only doping case shows that Pr3+‐codoping causes considerable change of Er3+ cross‐section value. In spectrally mixing regions of Er3+ and Pr3+, Pr3+ emission affects little the determination of Er3+ emission cross‐section as Pr3+ fluorescence is much weaker than Er3+ fluorescence due to low Pr3+ concentration.
Preparation of transparent Y2O3 ceramic via gel casting: Realization of high solid volume via surface modificationLiu, Wei; Jin, Lingling; Wang, Shiwei
doi: 10.1111/jace.16555pmid: N/A
In this article, isocyanate was adopted to modify Y2O3 powder for the purpose of preparing transparent Y2O3 ceramics via gel casting. The modification could enhance the hydration resistance of Y2O3 powder through the steric hindrance effect. The coating mechanism can be proved by the infrared spectrum of the surface‐modified Y2O3 powder. Modification could not only prevent Y2O3 particles from reacting with water, but also prevents agglomeration between particles. The viscosity of the slurry with a solid content of 52.7 vol% is only 0.48 Pa·s at the shear rate of 100 s−1, which is suitable for preparing high‐density compacts by gel casting. The transmittance of the sample (1840°C × 8 h, 1 mm thickness) at 1100 nm reaches 75%. The microstructure of the sintered body is dense with the average grain size of 6.5 μm without obvious impurities nor pores. Five mol% ZrO2‐doped Y2O3 transparent ceramic fairing with the diameter of 5 cm without defects was successfully fabricated by gel casting (52.7 vol% solid volume) and vacuum sintering (1840°C × 8 h).
Boosting piezoelectric response of KNN‐based ceramics with strong visible‐light absorptionZhong, Haoyin; Xiao, Hongyuan; Jiao, Nan; Guo, Yiping
doi: 10.1111/jace.16618pmid: N/A
A series of (1 − x)(K0.48Na0.52)NbO3‐x(Bi0.5Na0.5)(Zr0.55Ni0.45)O3‐δ (KNN‐BNZN) ceramics are designed to achieve excellent piezoelectric response along with narrow bandgap. The ceramics with x = 0.04 exhibit unprecedented piezoelectric coefficient d33 ~ 318±10pC N−1 in comparison with all reported narrow bandgap ceramics. A rhombohedral‐orthorhombic‐tetragonal (R‐O‐T) phase boundary is observed, indicating the formation of defect dipoles (Ni2+‐Vo¨) at morphotropic phase boundary region is desirable for piezo‐/ferroelectric properties. In addition, a narrow bandgap ~2.5 eV along with gap states (~0.9 eV and ~1.6 eV) is obtained from the ceramics when x > 0.02, which can be persuasively explained by the schematic plot of bandgap splitting mechanism proposed in this work, where Ni 3d energy state plays a role as a scaffold in the process of electron transition. More importantly, largely enhanced photovoltaic performance of the ceramics is achieved under AM 1.5 irradiation. The NIR photoresponse property (maximum current density of ~100 nA cm−2) indicates such KNN‐based ceramics with sub bandgap ~ 0.9 eV may even have potential to be applied in NIR light‐activated devices. Our findings might pave way for the further development of piezoelectric/photoresponsive multifunctional devices.
Selection principle of the synthetic route for fabrication of HfB2 and HfB2‐SiC ceramicsZhu, Qi‐Qi; Zhang, Yan; Guo, Wei‐Ming; Sun, Shi‐Kuan; Lin, Hua‐Tay
doi: 10.1111/jace.16627pmid: N/A
Densification, microstructure, and mechanical properties of spark plasma sintered HfB2 and HfB2‐SiC ceramics using HfB2 powders from borothermal reduction and boro/carbothermal reduction were investigated and compared. It was found that HfB2ceramics obtained by boro/carbothermal reduction exhibited a significantly higher sinterability compared to that by borothermal reduction. Inversely, HfB2‐SiC ceramics obtained by borothermal reduction exhibited a refined microstructure and better mechanical properties (Vickers hardness: 23.60 ± 2.43 GPa; fracture toughness: 5.89 ± 0.30 MPa.m1/2) than that by boro/carbothermal reduction. These results indicated that optimal fabrication of HfB2‐based ceramics could be achieved by the selection of synthetic route of HfB2 powders.
Characterization of micro‐mechanical properties of AlON ceramic by cantilever bending testDing, Maomao; Robertson, Stuart; Wang, Tun; Fan, Lingcong; Sun, Zehan; Maerz, Benjamin; Crookes, Robert; Xie, Jianjun; Shi, Ying; Wu, Houzheng
doi: 10.1111/jace.16614pmid: N/A
The AlON transparent ceramic cantilever beams containing twin and grain boundaries were fabricated by focused ion beam technique. The deformation behaviors were investigated by measurement of the load and displacement dependence of cantilever beams from micro bending tests. Young's modulus of AlON transparent ceramics was calculated from load and displacement curves, the results of which were consistent with results of previous works. Moreover, the bonding strengths of twin lamella boundary, twin boundary, and normal grain boundary in AlON transparent ceramics were 5.00, 5.05, and 4.81 GPa, respectively.
Effect of palladium on the microstructure and grain boundary complexions in SiCNavarro‐Solís, David J.; Cancino‐Trejo, Félix; López‐Honorato, Eddie
doi: 10.1111/jace.16622pmid: N/A
One of the main challenges in the study of TRISO (Tristructural Isotropic) coated fuel particles is the understanding of the diffusion of fission products through SiC. Among the elements produced inside the uranium kernel, it has been suggested that Pd might enhance the diffusion of other fission products. In this work, we have studied the interaction between Pd and SiC. We have observed that as Pd diffuses it can change the chemical composition and microstructure of SiC. Electron Backscattered Diffraction (EBSD) analysis showed that Pd increased the amount of high angle grain boundaries from 47% to 59%. Furthermore, we have observed that as Pd diffused, it changed the composition of SiC by leaving a trail of excess carbon at the grain boundary. This change in localized chemical composition and microstructure suggests a grain boundary complexion transition induced by Pd and a new way in which Pd can lead to faster diffusion routes for other fission products.
Reactive flash sintering of powders of four constituents into a single phase of a complex oxide in a few seconds below 700°CAvila, Viviana; Raj, Rishi
doi: 10.1111/jace.16625pmid: N/A
Recent work on reactive flash sintering of powders of two oxides, bismuth and of iron oxide, into pure single phase bismuth ferrite, which was accomplished in a few seconds at low furnace temperatures, is expanded to four constituents, alumina, lithia, zirconia, and lanthana, to produce reasonably dense polycrystals of a predominantly single phase, cubic LLZO(Al). Transformation and sintering occur concurrently at a furnace temperature near 700°C, in ambient atmosphere, in just a few seconds. The process may simplify the preparation of complex ceramics with new chemistries and dopants, which are predicted from ab intio calculations to have special attributes, not only because the powders sinter quickly at low temperatures, but also because the need for stoichiometric powders as starting materials is obviated.