Novel nanorod precipitate formation in neodymium and titanium codoped bismuth ferrite

The discovery of unusual nanorod precipitates in bismuth ferrite doped with Nd and Ti is reported. The atomic structure and chemistry of the nanorods are determined using a combination of high angle annular dark field imaging, electron energy loss spectroscopy, and density functional calculations. It is found that the structure of the BiFeO3 matrix is strongly modified adjacent to the precipitates; the readiness of BiFeO3 to adopt different structural allotropes in turn explains why such a large axial ratio, uncommon in precipitates, is stabilized. In addition, a correlation is found between the alignment of the rods and the orientation of ferroelastic domains in the matrix, which is consistent with the system's attempt to minimize its internal strain. Density functional calculations indicate a finite density of electronic states at the Fermi energy within the rods, suggesting enhanced electrical conductivity along the rod axes, and motivating future investigations of nanorod functionalities

Local stabilisation of polar order at charged antiphase boundaries in antiferroelectric (Bi_0.85Nd_0.15)(Ti_0.1Fe_0.9)O₃

Observation of an unusual, negatively-charged antiphase boundary in (Bi<sub>0.85</sub>Nd<sub>0.15</sub>)(Ti<sub>0.1</sub>Fe<sub>0.9</sub>)O<sub>3</sub> is reported. Aberration corrected scanning transmission electron microscopy is used to establish the full three dimensional structure of this boundary including O-ion positions to ~ ± 10 pm. The charged antiphase boundary stabilises tetragonally distorted regions with a strong polar ordering to either side of the boundary, with a characteristic length scale determined by the excess charge trapped at the boundary. Far away from the boundary the crystal relaxes into the well-known Nd-stabilised antiferroelectric phase

Drivers of U.S. toxicological footprints trajectory 1998–2013

By exploiting data from the Toxic Release Inventory of the United States, we have established that the toxicological footprint (TF) increased by 3.3% (88.4 Mt) between 1998 and 1999 and decreased by 39% (1088.5 Mt) between 1999 and 2013. From 1999 to 2006, the decreasing TF was driven by improvements in emissions intensity (i.e. gains in production efficiency) through toxic chemical management options: cleaner production; end of pipe treatment; transfer for further waste management; and production scale. In particular, the mining sector reduced its TF through outsourcing processes. Between 2006 and 2009, decreasing TF was due to decrease in consumption volume triggered by economic recession. Since 2009, the economic recovery increased TF, overwhelming the influence of improved emissions intensity through population growth, consumption and production structures. Accordingly, attaining a less-toxic economy and environment will be influenced by a combination of gains in production efficiency through improvement in emissions mitigation technologies and changes in consumption patterns. Overall, the current analysis highlights the structural dynamics of toxic chemical release and would inform future formulation of effective mitigation standards and management protocols towards the detoxification of the environmen

The effect of substrate clamping on the paraelectric to antiferroelectric phase transition in Nd-doped BiFeO₃ thin films

Thin films were deposited on Pt/Ti/SiO₂/Si substrates using pulsed laser deposition from a target with a composition (Bi₀.₈₂₅Nd₀.₁₇₅Fe₀.₉₇Ti₀.₀₃O₃) with 5 mol% excess Bi₂O₃ within the antiferroelectric (AFE) region of the NdFeO₃-BiFeO₃ phase diagram. However, Raman spectroscopy and transmission electron microscopy (TEM) revealed that films consisted of a mosaic microstructure in which (AFE), ferroelectric (FE) and paraelectric (PE) phases coexisted. Variation in the spatial distribution of Nd is typically greater in bulk ceramics than in thin films and therefore, the absence of single phase AFE cannot be attributed to local changes in composition. Instead, it is proposed that clamping due to mismatch in thermal expansion coefficient with the substrate suppresses the large volume change associated with the PE-FE and PE-AFE transition in bulk and its absence in the thin film prevents an avalanche-like transition throughout grains, which in bulk sustains single phase AFE, irrespective of local deviations in the Nd concentration

Temperature stable cold sintered (Bi0.95Li0.05)(V0.9Mo0.1)O4-Na2Mo2O7 microwave dielectric composites

Dense (Bi0.95Li0.05)(V0.9Mo0.1)O4-Na2Mo2O7 (100−x) wt.% (Bi0.95Li0.05)(V0.9Mo0.1)O4 (BLVMO)-x wt.% Na2Mo2O7 (NMO) composite ceramics were successfully fabricated through cold sintering at 150 °C under at 200 MPa for 30 min. X-ray diffraction, back-scattered scanning electron microscopy, and Raman spectroscopy not only corroborated the coexistence of BLVMO and NMO phases in all samples, but also the absence of parasitic phases and interdiffusion. With increasing NMO concentration, the relative pemittivity (εr) and the Temperature Coefficient of resonant Frequency (TCF) decreased, whereas the Microwave Quality Factor (Qf) increased. Near-zero TCF was measured for BLVMO-20wt.%NMO composites which exhibited εr ~ 40 and Qf ~ 4000 GHz. Finally, a dielectric Graded Radial INdex (GRIN) lens was simulated using the range of εr in the BLVMO-NMO system, which predicted a 70% aperture efficiency at 26 GHz, ideal for 5G applications

Cold sintered CaTiO3-K2MoO4 microwave dielectric ceramics for integrated microstrip patch antennas

CaTiO3-K2MoO4 (CTO-KMO) dielectric composites were successfully cold-sintered at 150 °C for 30 min with a uniaxial pressure of 200 MPa. X-ray diffraction, Raman spectroscopy, back-scattered SEM and energy dispersive x-ray mapping confirmed the coexistence of CTO and KMO with no evidence of interdiffusion and parasitic phases either between the two ceramic end-members or with Ag internal electrodes. As KMO concentration increased, the temperature coefficient of resonant frequency (TCF) and relative pemittivity (εr) decreased but the microwave quality factor (Q × f) increased. A near-zero TCF composition was obtained for CTO-0.92KMO composites which exhibited εr ∼ 8.5 and Q × f ∼ 11,000 GHz. A microstrip patch antenna was designed and fabricated using cold sintered CTO-0.92KMO as a substrate (40×40×1.4 mm), which gave a s11 of −14.2 dB and a radiation efficiency of 62.0 % at 2.51 GHz

Multi-material additive manufacturing of low sintering temperature Bi2Mo2O9 ceramics with Ag floating electrodes by selective laser burnout

Additive manufacturing (AM) of co-fired low temperature ceramics offers a unique route for fabrication of novel 3D radio frequency (RF) and microwave communication components, embedded electronics and sensors. This paper describes the first-ever direct 3D printing of low temperature co-fired ceramics/floating electrode 3D structures. Slurry-based AM and selective laser burnout (SLB) were used to fabricate bulk dielectric, Bi2Mo2O9 (BMO, sintering temperature = 620–650°C, εr = 38) with silver (Ag) internal floating electrodes. A printable BMO slurry was developed and the SLB optimised to improve edge definition and burn out the binder without damaging the ceramic. The SLB increased the green strength needed for shape retention, produced crack-free parts and prevented Ag leaching into the ceramic during co-firing. The green parts were sintered after SLB in a conventional furnace at 645°C for 4 h and achieved 94.5% density, compressive strength of 4097 MPa, a relative permittivity (εr) of 33.8 and a loss tangent (tan δ) of 0.0004 (8 GHz) for BMO. The feasibility of using SLB followed by a post-printing sintering step to create BMO/Ag 3D structures was thus demonstrated

Are lead-free piezoelectrics more environmentally friendly?

Considered as a less hazardous piezoelectric material, potassium sodium niobate (KNN) has been in the fore of the search for replacement of lead (Pb) zirconate titanate for piezoelectrics applications. Here, we challenge the environmental credentials of KNN due to the presence of ~60 wt% Nb2O5, a substance much less toxic to humans than Pb oxide, but whose mining and extraction cause significant environmental damage

The fourteenth-century poll tax returns and the study of English surname distribution

The modern-day distributions of English surnames have been considered in genealogical, historical, and philological research as possible indicators of their origins. However, many centuries have passed since hereditary surnames were first used, and so their distribution today does not necessarily reflect their original spread, misrepresenting their origins. Previously, medieval data with national coverage have not been available for a study of surname distribution, but with the recent publication of the fourteenth-century poll tax returns, this has changed. By presenting discrepancies in medieval and nineteenth-century distributions, it is shown that more recent surname data may not be a suitable guide to surname origins and can be usefully supplemented by medieval data in order to arrive at more accurate conclusions