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While BiFeO3-based solid solutions show great promise for applications in energy conversion and storage, realizing this promise necessitates understanding the structure-property relationship in particular pertaining to the relaxor-like characteristics often exhibited by solid solutions with polar-to-non-polar morphotropic phase boundaries. To this end, we investigated the role of the compositionally-driven relaxor state in (100-x)BiFeO3-xSrTiO3 [BFO-xSTO], via in situ synchrotron X-ray diffraction under bipolar electric-field cycling. The electric-field induced changes to the crystal structure, phase fraction and domain textures were monitored via the {111}pc, {200}pc, and 1/2{311}pc Bragg peaks. The dynamics of the intensities and positions of the (111) and (11-1) reflections reveal an initial non-ergodic regime followed by long-range ferroelectric ordering after extended poling cycles. The increased degree of random multi-site occupation in BFO-42STO compared to BFO-35STO is correlated with an increase of the critical electric field needed to induce the non-ergodic-to-ferroelectric transition, and a decrease in the degree of domain reorientation. Although both compositions show an irreversible transition to a long-range ferroelectric state, our results suggest that the weaker ferroelectric response in BFO-42STO is related to an increase in ergodicity. This, in turn, serves to guide the development of BFO-based systems into promising platform for further property engineering towards specific capacitor applications.

Plastic crystals are supramolecular materials that possess a unique high entropy mesophase at elevated temperatures, where a long-range structural symmetry coexists with a local molecular orientational disorder. The transition to mesophase can involve a large entropy change useful for thermal energy storage and influences the temperature range of ferroelectric and piezoelectric properties, important for sensor applications. Synchrotron X-ray diffraction and pair distribution function analysis were used to study the structure, while calorimetry, dielectric, leakage current measurements, and density functional theory were used to investigate the influence of the organic cation on the structure and properties of tetraethylammonium bromotrichloroferrate(III) [(C2H5)4N][FeBrCl3] and tetramethylammonium bromotrichloroferrate [(CH3)4N][FeBrCl3]. The [(C2H5)4N][FeBrCl3] mesophase transition had an entropy change of 151.5 J·K–1·kg–1, while [(CH3)4N][FeBrCl3] had only 49 J·K–1·kg–1. This was explained by the [(C2H5)4N][FeBrCl3] mesophase having less long-range structural symmetry and more local orientational disorder, of both the cations and anions, compared to [(CH3)4N][FeBrCl3]. Both materials exhibited at least two conductive mechanisms below the transition, vacancy-mediated ionic and electronic conduction. The introduction of anion orientational freedom, as opposed to cation orientational freedom, at the mesophase transition was most influential for the electrical properties.

Plastic ionic molecular crystals are a novel class of materials that have attracted recent interest due to the discovery of ferroelectric and piezoelectric properties together with an orientationally disordered mesophase with high plasticity. Despite the growing interest, little is known about the mechanisms that underpin their piezoelectric properties. To address this knowledge gap, we study the dielectric, piezoelectric and elastic properties of eleven plastic ionic molecular crystals using van der Waals density functional theory. The piezoelectric coefficients were found to reach values comparable to inorganic piezoelectrics. Further, some plastic crystals have strikingly large piezoelectric anisotropies. For HQReO4 (Quinuclidinium perrhenate) an anisotropy of |d 16 /d 33 | = 119 was found, 11 times that of LiNbO3, a phase pure inorganic noted for its anisotropy. Our study links the anisotropy to rotational motion of the constituent molecules in response to shear stress. The large shear piezoelectric coefficients, yet modest dielectric permittivity results in coupling coefficients – a measure of its suitability for energy harvesting – with values up to 0.79. Our study points to the engineering of the rotational response of plastic ionic crystals as key to realizing the outstanding functional properties of these compounds.

Ferroelectric films are often constrained by their substrates and subject to scaling effects, including suppressed dielectric permittivity. In this work, the thickness dependence of intrinsic and extrinsic contributions to the dielectric properties was elucidated. A novel approach to quantitatively deconstruct the relative permittivity into three contributions (intrinsic, reversible extrinsic, and irreversible extrinsic) was developed using a combination of X-ray diffraction (XRD) and Rayleigh analysis. In situ synchrotron XRD was used to understand the influence of residual stress and substrate clamping on the domain state, ferroelastic domain reorientation, and electric field-induced strain. For tetragonal {001} textured Pb0.99(Zr0.3Ti0.7)0.98Nb0.02O3 thin films clamped to an Si substrate, a thickness-dependent in-plane tensile stress developed during processing, which dictates the domain distribution over a thickness range of 0.27– $1.11~\mu \text{m}$ . However, after the films were partially declamped from the substrate and annealed, the residual stress was alleviated. As a result, the thickness dependence of the volume fraction of ${c}$ -domains largely disappeared, and the out-of-plane lattice spacings ( ${d}$ ) for both ${a}$ - and ${c}$ -domains increased. The volume fraction of ${c}$ -domains was used to calculate the intrinsic relative permittivity. The reversible Rayleigh coefficient was then used to separate the intrinsic and reversible extrinsic contributions. The reversible extrinsic response accounted for ~50% of the overall relative permittivity (measured at 50 Hz and alternating current (ac) field of $0.5\cdot {E}_{c}$ ) and was thickness dependent even after poling and upon release.

Bi0.88Gd0.12FeO3 multiferroics are of interest for next-generation electronics and are shown with a remnant magnetization 0.2 emu·g−1, coercive field 8 kOe, Curie temperature 370 °C and magnetization of 0.7 emu·g−1 at magnetic fields 30 kOe. Scanning probe microscopy confirmed the intrinsic multiferroicity in the perovskite phase with coexistence of ferroelectric/ferroelastic and ferromagnetic domain structures. Strong magnetic hysteresis was produced by thermal cycling to 1000 °C due to degeneration of the perovskite phase into iron oxide inclusions, highlighting the importance of processing, thermal history and thermodynamic stability for minimizing the amount of parasitic magnetic secondary phases. This is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Ionic plastic crystals are part of an emerging class of hybrid organic–inorganic ferroelectrics. The combination of low dielectric constants ( 100 pC N−1) and low temperature synthesis make ferroelectric plastic crystals strong candidates for sensing and energy harvesting applications so more research of the electrical properties, such as dielectric loss and super-coercive hysteresis is needed. Tetramethylammonium bromotrichloroferrate(III) was studied as a prototypical material and a non-centrosymmetric orthorhombic Amm2 structure was confirmed by X-ray diffraction at room temperature. The relative permittivity was below 20 at high frequencies (105 Hz) but high dielectric losses at frequencies 80 to 30 kV cm−1 and 0.046 to 0.017% respectively between 100 and 0.1 Hz. At 100 Hz the material exhibited a strong asymmetric hysteresis that was reversible depending on the electric field direction. The observed behavior was consistent with a defect pinning model of ferroelectric switching behavior and thus some likely point defect species were proposed and thought to result from solution non-stoichiometry or residual moisture and solvent.

The displacement of urban households and livelihoods by state institutions is typically justified on the basis of the developmental purposes of land clearance, purportedly in the public interest. H...

The rising cost of energy and concerns about the environmental impact of manufacturing processes have necessitated the need for more efficient and sustainable manufacturing. The ceramic industry is an energy intensive industrial sector and consequently the potential to improve energy efficiency is huge, particularly through the introduction of modern sintering technologies. Although several energy efficient sintering processes have been developed, there is no comprehensive techno-economic analysis which compares and contrasts these techniques. This paper presents a critical review and analysis of a number of sintering techniques and compares them with the recently developed cold sintering process (CSP), including mode of operation, sintering mechanism, typical heating rates, duration of sintering, energy consumption profile and energy saving potential, limitations, key challenges for further development and current research efforts. By using a figure of merit, pounds per tonne of CO2 saved (£/tCO2-eq), which links initial capital investment with energy savings, within a framework derived from ranking principles such as marginal abatement cost curves and Pareto optimisation, we have demonstrated that under the scenarios considered for 3 separate functional oxides ZnO, PZT and BaTiO3, CSP is the most economically attractive sintering option, indicating lower capital costs and best return on investment as well as considerable energy and emission savings. Although the current work establishes the viability of CSP as a competitive and sustainable alternative to other sintering techniques, the transition from laboratory to industry of CSP will require hugely different facilities and instrumentation as well as relevant property/performance validation to realise its full potential.

In this work, BiFeO3-SrTiO3 (BFO-STO) solid solutions have been studied with particular emphasis on the problems related to conventional solid state synthesis of BFO-based systems. This method results in the formation of Bi-rich phase on grain boundaries and inhomogeneities inside the grains, similar to the core-shell microstructure previously reported for several BFO-based ceramic systems. Highly homogeneous and dense BFO-STO ceramics were prepared by mechanochemical activation-assisted synthesis. The as-prepared (x)BFO-(1-x)STO ceramics with 0.7 ≥ x≥ 0.575 exhibited high remanent polarization (30–50 μC cm−2) and a maximum d33 value of 69 pC N-1 at x = 0.625. It is shown that the compositions in the close proximity of the pseudocubic phase (x ≤ 0.6), however, exhibit pronounced aging of d33 coefficient with time, which is most probably related to the low stability of the domain structure after poling. The results of this study could further promote the processing optimization and compositional design of the BFO-STO and other BFO-based systems.

Understanding the failure mechanisms of piezoelectric thin films is critical for the commercialization of piezoelectric microelectromechanical systems. This paper describes the failure of $0.6\ \mu \mathrm{m}$ lead zirconate titanate (PZT) thin films on Si wafers with different in-plane stresses under large electric fields. The films failed by a combination of cracking and thermal breakdown events. It was found that the crack initiation and propagation behavior varied with the stress state of the films. The total stress required for crack initiation was estimated to be near 500 MPa. As expected, cracks propagated perpendicular to the maximum tensile stress direction. Thermal breakdown events and cracks were correlated, suggesting coupling between electrical and mechanical failure. It was also found that films that were released from the underlying substrates were less susceptible to failure by cracking. It was proposed that during electric field loading the released film stacks were able to bow and alleviate some of the stress. Released films may also experience enhanced domain wall motion that increases their fracture toughness. The results indicate that both applied stress and clamping conditions play important roles in the electromechancial failure of piezoelectric thin films.

The data presented here is related to the research article titled “Evicting the poor in the ‘overriding public interest’: Crisis of rights and interests, and contestations in Nigerian cities” [1]. This data brief presents relevant national and sub-national data on patterns, trends, and impacts of reported urban infrastructure-related displacements in Nigeria between 2010 and 2016. The data of reported cases of displacements in Nigeria are presented in tabular matrix. On the horizontal side are nested rows designated as the six geopolitical zones (South East, South South, South West, North Central, North East, and North West), 36 States of the country, and Abuja Federal Capital Territory. It was also necessary to identify particular local government areas where displacements occurred or were imminent (case locations). On the vertical side, 14 columns itemized diverse variables such as type of infrastructure project, as well as the mode/type, status, and mechanisms of displacement. Other columns include reasons given for displacement, project funder/initiator, number of project affected persons (PAPs), reported social characteristics of PAPs, response of PAPs, actions/outcomes, information sources and link, date(s) of reported displacement in addition to a section for notes. Besides chronicling urban infrastructure-related displacement cases in the period under review, this brief might equally serve as a benchmark for a prospective national displacement register. It will also function as a useful information resource not only for facilitating advocacy and research in built environment disciplines and civil rights campaigns, but also serve to conscientize policy makers and development practitioners on the cumulative cost implications of displacement. Further interpretive insights could be achieved through data mining and cross-tabulation.

Domain-wall dynamics under strong, super-coercive electric fields in polycrystalline bismuth ferrite (BiFeO3) are not well established due to the experimental difficulties in processing high phase purity perovskite with low electrical conductivity. Overcoming these difficulties, here we present x-ray diffraction measurements carried out in situ during electrical poling with a trapezoidal electric-field to investigate the domain wall dynamics and lattice strain in this material. It is observed that during field ramping, microscopic strains, i.e., non-180° domain texture and lattice strain, increase simultaneously. During DC field dwell, however, a lattice strain decrease occurs over time, accompanied by an increase in the non-180° domain texture. This inverse time-dependent trend of microscopic strain mechanisms is speculated to be due to mobile charged defects residing in domain wall regions. The configuration of these charged point defects may also play a role in the observed post-poling relaxations of non-180° domain texture and macroscopic piezoelectric coefficients on removal of the field. Since conducting domain walls have been recently identified in a number of ferroelectrics, these results should significantly impact the understanding of strain mechanisms not only in BiFeO3 but on a broader range of ferroelectric materials. Locked until 23.3.2021 due to copyright restrictions. Published by AIP Publishing. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in JOURNAL and may be found at https://doi.org/10.1063/5.0002235

Tetramethylammonium bromotrichloroferrate(III) ([N(CH3)4][FeBrCl3]) is a plastic crystal ferroelectric with small dielectric constant

Rare earth modified bismuth ferrites are of interest as lead-free multiferroics, however reliable methods for reducing the electrical conductivity are needed. In this study ceramics with composition (Bi0.91Dy0.09)FeO3 were doped with 0.2 mol% cobalt (Co) and the impedance spectra, high electric field hysteresis and leakage current were compared to undoped ceramics. In pristine ceramics Co addition increased the bulk conductivity of the material but removed a relaxation from the dielectric loss and modulus in the frequency range 100 Hz–1 MHz. The remanent polarization and peak-to-peak strain of both ceramics were 38 µC/cm2 and 0.15% respectively, but surprisingly Co doped ceramics exhibited lower electrical leakage at above-coercive fields. Significant changes in the loss, modulus and leakage current of undoped ceramics after poling suggested that de-trapped charge carriers play a dominant role in the conductivity of undoped ceramics after poling. This effect was reduced by Co doping.

Scaling effects were investigated in tetragonal {001} textured Pb(Zr0·3Ti0.7)O3 thin films doped with 2 mol% Nb over a thickness range of 0.27 μm–1.11 μm. Scaling effects refer to the size-induced degradation of properties at length scales exceeding those associated with the ferroelectric stability limit. The irreversible Rayleigh coefficient was found to be thickness-dependent, indicating suppression of the extrinsic contributions to the relative permittivity for all clamped films. Both defects in the seed layer and substrate clamping contributed to the observed thickness dependence. The influence of the seed layer on dielectric properties was accounted for using a capacitor in series model. After the films were partially declamped from the substrate, the irreversible contributions increased up to 23% in Nb-doped films and became more frequency dependent (by up to 29%). The suppressed frequency dependence in the clamped films was attributed to the pinning of irreversible domain walls active at lower frequencies. Both the seed layer and substrate clamping contributed to the pinning of irreversible domain walls.

HSAC 840 steel rockbolts were examined, all of which had failed in service through the threaded region exterior to the rock face by brittle fracture transverse to the bolt axis. The bolts had been ...

Samarium-modified bismuth ferrite ((Bi,Sm)FeO3 or BSFO) is a room-temperature multiferroic with a morphotropic phase boundary near 15.5 mol% Sm, where ferroelectric, antiferroelectric and paraelectric phases coexist and the electromechanical response (Smax/Emax and d33) is maximized. Recently, an electric field induced phase transformation was discovered, which is believed to play a significant role in the macroscopic electromechanical response. Here, we used in situ synchrotron X-ray powder diffraction to directly measure this transformation in real time within bulk ceramics to determine the dynamics, structural pathway and crystallographic orientation dependence of the transformation. Our results show that there are two transformation pathways; an antiferroelectric-to-ferroelectric transformation, which is revesible, and a paraelectric-to-ferroelectric transformation, which is irreversible. Furthermore, these transformations occur with a strong orientation dependence with respect to the applied electric field direction, and with extremely slow dynamics – just 2 to 10 minutes – orders of magnitude longer than in other ferroelectrics (e.g. Bi1/2Na1/2TiO3–BaTiO3 or BNT–BT). These findings point to texturing and the elimination of the paraelectric phase to enhance the electromechanical response. Moreover, they provide a detailed picture of the transformation dynamics and a greater understanding of electric field induced transformations in ferroelectric ceramics.

Young people in care are known to have high levels of aggressive behaviors and high levels of self-esteem, and these difficulties continue into adult life. Previous research has suggested that there is a relationship between self-esteem and aggression, although the nature of this relationship is unclear and possible differences due to gender have rarely been explored. Therefore, the relationships between different forms of self-esteem (global self-esteem, social rank, social fit, and attractiveness) and aggression were investigated in a sample of young care-leavers. For men, high levels of social rank and high levels of attractiveness were predictive of aggression, whereas for women low levels of perceived social inclusion and low levels of attractiveness were predictive of aggression. These findings suggest that there are significant gender differences in the relationship between self-esteem and aggression in care-leavers and that using domain-specific measures of self-esteem provides a richer understanding of these relationships. They also suggest that a more targeted approach to intervention is needed.

The latest government policies for personality disordered offenders emphasise the importance of a formulation-based approach to rehabilitation and pathway planning. However, research into forensic ...

The domain structure and local polarization reversal were studied in lead-free ceramics (K0.5Na0.5)1-2xSrxNbO3 by various modes of scanning probe microscopy. It was shown that the increase in Sr concentration led to a decrease in both grain and domain sizes. The local polarization reversal study provided important information on the domain wall dynamics in this complicated system. The defect distribution in doped ceramics was proposed as a major factor limiting domain wall mobility and internal bias field decrease together with the increase of the activation field for domain wall motion.

Piezoelectric properties and ferroelectric/ferroelastic domain switching behavior of polycrystalline ceramics are strongly influenced by local scale (i.e.

Purpose The purpose of this paper is to explore the views of NHS England (NHSE) and Her Majesty’s Prison and Probation Service (HMPPS) commissioners about the Offender Personality Disorder (OPD) pathway. Design/methodology/approach A thematic analysis of four semi-structured interviews with NHSE and HMPPS commissioners is conducted. Findings Commissioners offered a cautious but confident assessment of the potential effectiveness of the OPD pathway, drawing particular attention to its potential to enhance the confidence and competency of staff, offer better value for money and provide enhanced progression routes for offenders with personality disorders. Additionally, commissioners identified a number of potential risks for the pathway including wider system flux, funding availability, multi-agency working, offender engagement and the need to evidence effectiveness. Research limitations/implications The analysis is based on a small number of interviews. However, there are only a limited number of commissioners involved with the OPD pathway. Practical implications While the stronger focus on progression in the OPD pathway is a welcome departure from a narrow focus on high security Dangerous and Severe Personality Disorder (DSPD) services, the foundations of the OPD pathway ultimately lie with the DSPD programme and similar challenges are likely to follow. The system within which the pathway operates is subject to a great deal of flux and this inevitably poses significant challenges for pathway services, staff and offenders, as well as for those of us charged with its evaluation. Originality/value There has been limited empirical work with commissioners in the mental health field. The paper offers a unique insight into the perspectives of those responsible for commissioning the OPD pathway.

BACKGROUND Mental health services aim to provide recovery-focused care and facilitate coproduced care planning. In practice, mental health providers can find supporting individualized coproduced care with service users difficult while balancing administrative and performance demands. To help meet this aim and using principles of coproduction, an innovative mobile digital care pathway tool (CPT) was developed to be used on a tablet computer and piloted in the West of England. OBJECTIVE The aim of this study was to examine mental health care providers’ views of and experiences with the CPT during the pilot implementation phase and identify factors influencing its implementation. METHODS A total of 20 in-depth telephone interviews were conducted with providers participating in the pilot and managers in the host organization. Interviews were audio recorded, transcribed, anonymized, and thematically analyzed guided by the Consolidated Framework for Implementation Research. RESULTS The tool was thought to facilitate coproduced recovery-focused care planning, a policy and organizational as well as professional priority. Internet connectivity issues, system interoperability, and access to service users’ health records affected use of the tool during mobile working. The organization’s resources, such as information technology (IT) infrastructure and staff time and IT culture, influenced implementation. Participants’ levels of use of the tool were dependent on knowledge of the tool and self-efficacy; perceived service-user needs and characteristics; and perceptions of impact on the therapeutic relationship. Training and preparation time influenced participants’ confidence in using the tool. CONCLUSIONS Findings highlight the importance of congruence between staff, organization, and external policy priorities and digital technologies in aiding intervention engagement, and the need for ongoing training and support of those intended to use the technology during and after the end of implementation interventions.

The importance of assistive technology (AT) is gaining recognition, with the World Health Organisation (WHO) set to publish a Global Report in 2022. Yet little is understood about access for the poorest, or the potential of AT to enable this group to participate in the activities of citizenship, both formal and informal. The aim of this qualitative study was to explore AT as mediator of participation in citizenship for persons with disabilities who live in two informal settlements in Freetown, Sierra Leone (SL). The paper presents evidence from 16 participant and 5 stakeholder interviews, 5 focus groups and 4 events, combining this with the findings of a house-to-house AT survey, and two national studies—a country capacity assessment and an informal markets deep-dive. Despite citizenship activities being valued, a lack of AT was consistently reported and hindered participation. Stigma was also found to be a major barrier. AT access for the poorest must be addressed if citizenship participation for persons with disabilities is a genuine global intention and disability justice is to become a reality.

Rapid urbanisation is precipitating wide-ranging and often irreversible changes in cities and at the shifting peri-urban areas around the world. As a significant factor of change in the 21st Century, urbanisation is irreversibly transforming everything on its path―air, land, water, and ecology, including institutions, customs, and lifestyles. The subject scope of urbanisation research is therefore quite wide and diverse. Yet, urbanisation-induced attritions and substitutions of customary tenure practices, coupled with the associated politics and resistances, remain utterly overlooked. Using a mixed method approach (involving desktop research, remote sensing data and stakeholder interviews), this paper examines the clashes between customary tenure regime and statutory practices dictated by urban laws, and how different stakeholders are appropriating them both to promote and resist displacement or eviction. Amidst growing encroachment pressures on peri-urban communities in Nigerian cities, a new imperative for enhanced tenure security and integrated planning approach are proposed.

This study presents microstructural and phase compositional characterization of 30-μm-thick bismuth ferrite (BiFeO3) films screen-printed on Ag, Au and Pt metal foils. Ag is shown to be chemically incompatible with BiFeO3 at temperatures higher than 750°C. X-ray diffraction and scanning electron microscopy analysis reveal that an almost single phase BiFeO3 thick film can be obtained on Au and Pt substrates after sintering at 750°C, while sintering at 820°C results in increased densification of BiFeO3. This work represents another step further towards the integration of BiFeO3 into thick film structures.

This study presents the preparation of bismuth ferrite (BiFeO 3 ) thick films by a screen-printing method. We explain the influence of the annealing temperature on the diffusion processes, occurring through individual layers of the thick-film structure, densification, and interface reactions between ∼15-μm-thick BiFeO 3 films and an Al 2 O 3 substrate. The key parameters were identified and include the optimal annealing temperature and substrate purity, which need to be controlled in order to obtain high quality BiFeO 3 thick films in terms of phase composition and microstructure. Taking into account these processing parameters, we present compositionally improved and high density BiFeO 3 thick films on Ag metal foil, which were sintered at temperatures as low as 740 °C. While the local ferroelectric behavior of the BiFeO 3 film has been confirmed by piezo-response force microscopy analysis, its macroscopic electrical response is characterized by a high electrical conductivity coupled with an interface-related diode-like current–voltage behavior.