Structural integrity and characteristics at lattice and nanometre levels of ZrN polycrystalline irradiated by 4 MeV Au ions

We report an as-hot-pressed zirconium nitride polycrystalline with its primary crystal structure maintained no change but lattice defects and features were introduced at nanometre-scale after being irradiated by 4 MeV Au 2+ with a total fluence of 5 × 10 16 /cm 2 . The variation of grey-level seen in backscattered electron images and electron backscattered diffraction maps directly evidenced the structure integrity of the polycrystalline ZrN is well maintained with no crystal structure change of ZrN. The irradiation depth had no relevance to crystal orientation, and Au deposition peaked at a depth of ∼0.58 μm with a near-Gaussian distribution. Within a depth < 0.58 μm, long dislocation lines were developed with a Burgers vector of [01¯] b /2 and density 3.2 × 10 14 1/m 2 ; beyond this depth, dislocation loops were formed with much higher density. In the ionization zone, cubic ZrO 2 crystallites precipitated in a size of ∼5 nm. The irradiation damage processes are discussed based on the observed features

In situ poling X-ray diffraction studies of lead-free BiFeO3–SrTiO3 ceramics

The origin of the large electrostrain in BiFeO3-BaTiO3 (BF-BT) ceramics is controversial and has been attributed to either a field-induced transition to a long-range ferroelectric (FE) state or to multi-symmetry, polar nanoregions within a pseudocubic matrix whose vectors approximately align with the direction of the applied field. The (1-x)BiFeO3-xSrTiO3 (BF-xST) solid solution is structurally and microstructurally similar to BF-BT and provides a further case study to assess the origin of electrostrain. In BF-xST, electrostrain is optimized at x = 0.4 (0.15%) which zero field, room temperature full-pattern X-ray diffraction (XRD) Rietveld refinement and scanning/transmission electron microscopy suggest is composed of 15% rhombohedral (R) cores, surrounded by 85% pseudocubic (PC) shells. In-situ poling synchrotron XRD reveals that all peaks remain singlet and exhibit no change in full width half maximum up to 100 kV cm−1, confirming the absence of long-range FE order and the retention of short-range polar order, despite the large applied field. Strain anisotropy (calculated from individual peaks) of ε220 > ε111 > ε200 and the associated strain orientation distribution however, indicate the existence of local orthorhombic (O), R and tetragonal (T) symmetries. The data therefore imply the existence under poling of multi-symmetry polar nanoregions in BF-0.4ST rather than a long FE phase, supporting the model described by Wang and co-workers (2019) for BF-BT compositions

Reduced He ion irradiation damage in ZrC-based high-entropy ceramics

Excellent irradiation resistance is the basic property of nuclear materials to keep nuclear safety. The high-entropy design has great potential to improve the irradiation resistance of the nuclear materials, which has been proven in alloys. However, whether or not high entropy can also improve the irradiation resistance of ceramics, especially the mechanism therein still needs to be uncovered. In this work, the irradiation and helium (He) behaviors of zirconium carbide (ZrC)-based high-entropy ceramics (HECs), i.e., (Zr0.2Ti0.2Nb0.2Ta0.2W0.2)C, were investigated and compared with those of ZrC under 540 keV He ion irradiation with a dose of 1×1017 cm−2 at room temperature and subsequent annealing. Both ZrC and (Zr0.2Ti0.2Nb0.2Ta0.2W0.2)C maintain lattice integrity after irradiation, while the irradiation-induced lattice expansion is smaller in (Zr0.2Ti0.2Nb0.2Ta0.2W0.2)C (0.78%) with highly thermodynamic stability than that in ZrC (0.91%). After annealing at 800 ℃, ZrC exhibits the residual 0.20% lattice expansion, while (Zr0.2Ti0.2Nb0.2Ta0.2W0.2)C shows only 0.10%. Full recovery of the lattice parameter (a) is achieved for both ceramics after annealing at 1500 ℃. In addition, the high entropy in the meantime brings about the favorable structural evolution phenomena including smaller He bubbles that are evenly distributed without abnormal coarsening or aggregation, segregation, and shorter and sparser dislocation. The excellent irradiation resistance is related to the high-entropy-induced phase stability, sluggish diffusion of defects, and stress dispersion along with the production of vacancies by valence compensation. The present study indicates a high potential of high-entropy carbides in irradiation resistance applications

FORT-1: Phase II/III Study of Rogaratinib Versus Chemotherapy in Patients With Locally Advanced or Metastatic Urothelial Carcinoma Selected Based on FGFR1/3 mRNA Expression

Purpose: Rogaratinib, an oral pan-fibroblast growth factor receptor (FGFR1-4) inhibitor, showed promising phase I efficacy and safety in patients with advanced urothelial carcinoma (UC) with FGFR1-3 mRNA overexpression. We assessed rogaratinib efficacy and safety versus chemotherapy in patients with FGFR mRNA-positive advanced/metastatic UC previously treated with platinum chemotherapy. Methods: FORT-1 (ClinicalTrials.gov identifier: NCT03410693) was a phase II/III, randomized, open-label trial. Patients with FGFR1/3 mRNA-positive locally advanced or metastatic UC with ≥ 1 prior platinum-containing regimen were randomly assigned (1:1) to rogaratinib (800 mg orally twice daily, 3-week cycles; n = 87) or chemotherapy (docetaxel 75 mg/m2, paclitaxel 175 mg/m2, or vinflunine 320 mg/m2 intravenously once every 3 weeks; n = 88). The primary end point was overall survival, with objective response rate (ORR) analysis planned following phase II accrual. Because of comparable efficacy between treatments, enrollment was stopped before progression to phase III; a full interim analysis of phase II was completed. Results: ORRs were 20.7% (rogaratinib, 18/87; 95% CI, 12.7 to 30.7) and 19.3% (chemotherapy, 17/88; 95% CI, 11.7 to 29.1). Median overall survival was 8.3 months (95% CI, 6.5 to not estimable) and 9.8 months (95% CI, 6.8 to not estimable; hazard ratio, 1.11; 95% CI, 0.71 to 1.72; P = .67). Grade 3/4 events occurred in 37 (43.0%)/4 (4.7%) patients and 32 (39.0%)/15 (18.3%), respectively. No rogaratinib-related deaths occurred. Exploratory analysis of patients with FGFR3 DNA alterations showed ORRs of 52.4% (11/21; 95% CI, 29.8 to 74.3) for rogaratinib and 26.7% (4/15; 95% CI, 7.8 to 55.1) for chemotherapy. Conclusion: To our knowledge, these are the first data to compare FGFR-directed therapy with chemotherapy in patients with FGFR-altered UC, showing comparable efficacy and manageable safety. Exploratory testing suggested FGFR3 DNA alterations in association with FGFR1/3 mRNA overexpression may be better predictors of rogaratinib response

Superior energy density through tailored dopant strategies in multilayer ceramic capacitors

The Gerson–Marshall (1959) relationship predicts an increase in dielectric breakdown strength (BDS) and therefore, recoverable energy density (Wrec) with decreasing dielectric layer thickness. This relationship only operates however, if the total resistivity of the dielectric is sufficiently high and the electrical microstructure is homogeneous (no short circuit diffusion paths). BiFeO3–SrTiO3 (BF–ST) is a promising base for developing high energy density capacitors but Bi-rich compositions which have the highest polarisability per unit volume are ferroelectric rather than relaxor and are electrically too conductive. Here, we present a systematic strategy to optimise BDS and maximum polarisation via: (i) Nb-doping to increase resistivity by eliminating hole conduction and promoting electrical homogeneity and (ii) alloying with a third perovskite end-member, BiMg2/3Nb1/3O3 (BMN), to reduce long range polar coupling without decreasing the average ionic polarisability. These strategies result in an increase in BDS to give Wrec = 8.2 J cm−3 at 460 kV cm−1 for BF–ST–0.03Nb–0.1BMN ceramics, which when incorporated in a multilayer capacitor with dielectric layers of 8 μm thickness gives BDS > 1000 kV cm−1 and Wrec = 15.8 J cm−3

Mechanism of enhanced energy storage density in AgNbO3-based lead-free antiferroelectrics

The mechanisms underpinning high energy storage density in lead-free Ag1–3xNdxTayNb1-yO3 antiferroelectric (AFE) ceramics have been investigated. Rietveld refinements of in-situ synchrotron X-ray data reveal that the structure remains quadrupled and orthorhombic under electric field (E) but adopts a non-centrosymmetric space group, Pmc21, in which the cations exhibit a ferrielectric configuration. Nd and Ta doping both stabilize the AFE structure, thereby increasing the AFE-ferrielectric switching field from 150 to 350 kV cm−1. Domain size and correlation length of AFE/ferrielectric coupling reduce with Nd doping, leading to slimmer hysteresis loops. The maximum polarization (Pmax) is optimized through A-site aliovalent doping which also decreases electrical conductivity, permitting the application of a larger E. These effects combine to enhance energy storage density to give Wrec = 6.5 J cm−3 for Ag0.97Nd0.01Ta0.20Nb0.80O3

Synthesis of zirconolite-2M ceramics for immobilisation of neptunium

Praseodymium-doped zirconolite ceramics targeting nominal composition Ca1-xPrxZrTi2-5x/3Al5x/3O7 (x ≤ 0.20, Δx = 0.05) were fabricated by a mixed oxide solid state reaction, at 1350 °C in air for 20 h. Praseodymium (Pr) was employed as a surrogate for neptunium (Np), with Al3+ co-accommodated to provide charge balance. High-resolution transmission electron microscopy and electron diffraction analyses confirmed that zirconolite crystallised as the 2 M monoclinic polytype throughout the phase evolution, with no evidence of transformation to other polytype structures. Phase assemblage and microstructural data were consistent with zirconolite occupying a high fraction of the phase assemblage (>ca. 93 wt %), alongside a minor secondary perovskite phase at all levels of targeted Pr incorporation. Despite this, it was demonstrated near theoretical density formed through a solid-state fabrication route, and we therefore propose that, through analogy with the corresponding Pr solid solution, zirconolite may be a suitable candidate for the immobilisation of Np-bearing wastes