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The mechanisms underpinning high energy storage density in lead-free Ag 1–3 x Nd x Ta y Nb 1- y O 3 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, Pmc2 1 , 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 (P max) 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 W rec = 6.5 J cm−3 for Ag 0.97 Nd 0.01 Ta 0.20 Nb 0.80 O 3. ga1 Schematic diagram illustrating how energy storage density is optimized through doping in AgNbO 3 and shedding light on the design of novel antiferroelectric (AFE) materials with excellent energy storage density. ● Excellent performance achieved for AgNbO 3 -based antiferroelectric lead-free energy storage ceramics. ● The first observation of a field induced ferrielectric phase. ● 4 principles proposed for the design of high energy density properties of AgNbO 3 -based antiferroelectric ceramics: i) increased resistivity, ii) optimization of maximum polarization, iii) decreased antipolar/polar coupling, and iv) enhanced AFE stability. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microscale resolution residual strain mapping inside porcelain veneer. • Pair distribution function X-ray diffraction quantification using new technique. • Ring-core focused ion beam and digital image correlation cross-validation. • Comparable results, with tensile strain maximum on inner surface. • Oscillatory strains associated with layering manufacture approach observed. Abstract Objective Residually strained porcelain is influential in the early onset of failure in Yttria Partially Stabilised Zirconia (YPSZ) – porcelain dental prosthesis. In order to improve current understanding it is necessary to increase the spatial resolution of residual strain analysis in these veneers. Methods Few techniques exist which can resolve residual stress in amorphous materials at the microscale resolution required. For this reason, recent developments in Pair Distribution Function (PDF) analysis of X-ray diffraction data of dental porcelain have been exploited. This approach has facilitated high-resolution (70 μm) quantification of residual strain in a YPSZ-porcelain dental prosthesis. In order to cross-validate this technique, the sequential ring-core focused ion beam and digital image correlation approach was implemented at a step size of 50 μm. This semi-destructive technique exploits microscale strain relief to provide quantitative estimates of the near-surface residual strain. Results The two techniques were found to show highly comparable results. The residual strain within the veneer was found to be primarily tensile, with the highest magnitude stresses located at the YPSZ-porcelain interface where failure is known to originate. Oscillatory tensile and compressive stresses were also found in a direction parallel to the interface, likely to be induced by the multiple layering used during fabrication. Significance This study provides the insights required to improve prosthesis modelling, to develop new processing routes that minimise residual stress and ultimately to reduce prosthesis failure rates. The PDF approach also offers a powerful new technique for microscale strain quantification in amorphous materials. [ABSTRACT FROM AUTHOR]

• Domain switching and lattice strain in polycrystalline K 0.5 Bi 0.5 TiO 3 -BiFeO 3 -PbTiO 3 is evaluated by in-situ high energy synchrotron XRD. • The tetragonal {200} grain family exhibited the highest effective lattice strain up to 8.2 × 10−3 at an electric field of 5 kV/mm. • A partial phase transformation from tetragonal to rhombohedral occurred at high electric field levels, with an average strain of −1.54 × 10−3. • Relaxation of intergranular stress gives rise to enhanced domain switching in KBT-BF-PT ceramics. • The observed self-adapting mechanism could also be exploited in other high performance, high temperature piezoelectric ceramics. We report an in-situ synchrotron X-ray diffraction study of K 0.5 Bi 0.5 TiO 3 -BiFeO 3 -PbTiO 3 ceramics, which exhibit a T c of around 450 °C. The electromechanical actuation mechanisms comprise contributions from coexisting tetragonal and rhombohedral phases. The tetragonal {200} grain family exhibited the highest effective lattice strain, up to 8.2 × 10−3 at 5 kV/mm. Strong strain anisotropy in the tetragonal phase and field-induced intergranular stresses facilitate a partial transformation from tetragonal (high strain anisotropy) to rhombohedral (low strain anisotropy) at high electric field levels, with an average linear transformation strain of -1.54 × 10-3. The domain switching behavior was effectively enhanced in both tetragonal and rhombohedral phases after the phase transformation, due to the release of intergranular stress. This observed self-adapting mechanism in tuning intergranular stress through partial phase switching in the morphotropic KBT-BF-PT composition with large lattice distortion could also be exploited in other perovskite systems in order to achieve high performance high temperature piezoelectric ceramics. [ABSTRACT FROM AUTHOR]

In situ Synchrotron Radiation X-ray Diffraction (SR-XRD) is employed to follow the evolution of corrosion products on X65 carbon steel in a CO 2 -containing aqueous environment (80 °C, pH 6.3–7.3). A custom-designed flow cell is used to follow the real-time concomitant changes in electrochemical behaviour and corrosion product growth during stages of both natural and potentiodynamically driven 'pseudo-passivation'. We show that no detectable crystalline magnetite (Fe 3 O 4) phase forms during 'pseudo-passivation' across all conditions studied. Furthermore, the results suggest the significant ennoblement observed during 'pseudo-passivation' in these experiments can be strongly related to the accumulation of iron carbonate (FeCO 3) on the steel surface. • Surface layers play a key role in pseudo-passivation of carbon steel. • Synchrotron radiation XRD employed in-situ with electrochemical techniques. • Investigation at 80 °C, in pH range from 6.3 to 7.3 in CO 2 environments. • Pseudo-passivation strongly linked to wide coverage of X65 steel by iron carbonate. • Magnetite (Fe 3 O 4) was not detected by SR-XRD under these conditions. [ABSTRACT FROM AUTHOR]

Abstract In the present study, we report a nonergodic relaxor ferroelectric composition for high temperature piezoelectric applications, 0.57BiFeO 3 -0.21K 0.5 Bi 0.5 TiO 3 -0.22PbTiO 3 , which exhibits T m around 420 °C. By combining the results of in-situ synchrotron XRD and strain measurements using digital image correlation, a pseudocubic nonergodic relaxor to rhombohedral ferroelectric transformation is identified, accompanied by a volume strain close to zero. A methodology is developed to determine the crystallographic parameters of the transformed rhombohedral ferroelectric phase in a strain-free state, using the invariant intersection for diffraction stress analysis. The phase transformation process was analyzed by methods combining peak profile fitting and full pattern refinement; the results obtained illustrate the strain arising from the phase transformation, together with intrinsic/extrinsic contributions and anisotropy in the field-induced strain. The study reveals unusual microscopic strain behavior, distinguished from that of normal rhombohedral ferroelectrics, showing the combined properties of ergodic and normal ferroelectric materials and leading to a dominant intrinsic lattice strain together with a weaker extrinsic domain switching effect. The elastic coupling between different grain families is also reflected in their similar strain orientation distribution (SOD) functions. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Abstract We report on laser-heated diamond anvil cell (LHDAC) experiments in the FeO–MgO–SiO 2 –CO 2 (FMSC) and CaO–MgO–SiO 2 –CO 2 (CMSC) systems at lower mantle pressures designed to test for decarbonation and diamond forming reactions. Sub-solidus phase relations based on synthesis experiments are reported in the pressure range of ∼35 to 90 GPa at temperatures of ∼1600 to 2200 K. Ternary bulk compositions comprised of mixtures of carbonate and silica are constructed such that decarbonation reactions produce non-ternary phases (e.g. bridgmanite, Ca-perovskite, diamond, CO 2 –V), and synchrotron X-ray diffraction and micro-Raman spectroscopy are used to identify the appearance of reaction products. We find that carbonate phases in these two systems react with silica to form bridgmanite ±Ca-perovskite + CO 2 at pressures in the range of ∼40 to 70 GPa and 1600 to 1900 K in decarbonation reactions with negative Clapeyron slopes. Our results show that decarbonation reactions form an impenetrable barrier to subduction of carbonate in oceanic crust to depths in the mantle greater than ∼1500 km. We also identify carbonate and CO 2 –V dissociation reactions that form diamond plus oxygen. On the basis of the observed decarbonation reactions we predict that the ultimate fate of carbonate in oceanic crust subducted into the deep lower mantle is in the form of refractory diamond in the deepest lower mantle along a slab geotherm and throughout the lower mantle along a mantle geotherm. Diamond produced in oceanic crust by subsolidus decarbonation is refractory and immobile and can be stored at the base of the mantle over long timescales, potentially returning to the surface in OIB magmas associated with deep mantle plumes. Highlights • Experiments were made in the systems FMS-CO2 and CMS-CO2 at lower mantle pressures. • Carbonate in these systems react with silica in the lower mantle. • Decarbonation reactions with negative P–T slopes form CO 2 or diamond plus oxygen. • Carbonate in oceanic crust is limited to ∼1500 km depth along subduction geotherms. • Diamond is the stable form of carbon in oceanic crust at ambient mantle temperature. [ABSTRACT FROM AUTHOR]

The templated grain growth technique was used to synthesise textured 60BiFeO 3 –40PbTiO 3 (60:40BFPT). Both Aurivillius (Bi 4 Ti 3 O 12 , PbBi 4 Ti 4 O 15 ) and perovskite templates (BaTiO 3 , SrTiO 3 ) were used to prepare 60:40BFPT. Only BaTiO 3 templates were found to successful impart a texture to the ceramic matrix. In the case of perovskite templates, ferroelectricity was evident from saturated polarisation hysteresis loops. Saturated polarisation loops were achieved due to the substitution of Ba 2+ or Sr 2+ , which reduces the coercive field. SrTiO 3 and BaTiO 3 templated ceramics showed remanent polarisation of 30 and 36 μC/cm 2 , respectively. Aurivillius templates did not generate ferroelectric materials. Because of their high chemical stability in this system, BaTiO 3 templates appear to be the best candidate for fabricating textured BFPT by the reactive templated grain growth method. [ABSTRACT FROM AUTHOR]