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Deterministic control of the intrinsic polarization state of ferroelectric thin films is essential for device applications. Independently of the well-established role of electrostatic boundary conditions and epitaxial strain, the importance of growth temperature as a tool to stabilize a target polarization state during thin film growth is shown here. Full control of the intrinsic polarization orientation of PbTiO3 thin films is demonstrated—from monodomain up, through polydomain, to monodomain down as imaged by piezoresponse force microscopy—using changes in the film growth temperature. X-ray diffraction and scanning transmission electron microscopy reveal a variation of c-axis related to out-of-plane strain gradients. These measurements, supported by Ginzburg–Landau–Devonshire free energy calculations and Rutherford backscattering spectroscopy, point to a defect mediated polarization gradient initiated by a temperature dependent effective built-in field during growth, allowing polarization control not only under specific growth conditions, but ex-situ, for subsequent processing and device applications.

CALF-20, [Zn2(1,2,4-triazolate)2(oxalate)] shows remarkable performance in post-combustion carbon capture, even under humid conditions1 but its reported crystal morphology hinders its applicability in mixed matrix membranes (MMMs). Here, a route to its preparation as platelets a few tens of nm thick is reported. These were incorporated into a PEBAX MH1567 polymer matrix and the resultant MMMs display improvement in CO2 permeability and CO2/N2 selectivity. [ABSTRACT FROM AUTHOR]

Exsolution of nanoparticles followed by chemical treatment ("chemistry at a point") is a very exciting approach to the smart design of functional materials such as visible light active photocatalysts. Unfortunately, the usually utilized thermal reduction approach is not feasible for low melting point metals and compounds such as Cd and CdO. Here a hydrothermal approach to prepare exsolved CdS nanodots on cotton ball‐like perovskite supports is described. The titanate‐based photocatalyst is synthesized using a hydrothermal process followed by room‐temperature sulfidation. The hydrothermal route directs A‐site doping of Cd2+ via hydroxyl group incorporation in the titanate lattice. Formation of CdS via exsolution provides a high H2 production mass activity of 3050 µmol g−1 h−1 under visible light with only 5 mol.% Cd doping of the titanate. Moreover, the strong CdS‐support interaction offers good cycling stability under UV–vis and visible light irradiation. This is the first report describing the exsolution of CdS nanodots at room temperature and shows its advantages for photocatalytic activity. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries have attracted widespread interest due to the potential for providing safe and cheap energy storage. However, large scale use of sodium‐ion batteries is limited by insufficient performance from positive electrode materials, while also avoiding the use of expensive and toxic elements. Here, we present a bi‐phasic sodium layered oxide material, O3/P2‐Na0.75Mn0.35Fe0.35Ti0.1Al0.1Cu0.1O2, free of Li, Ni, and Co, which delivered high energy densities up to 420 Wh kg−1, discharge potential of 3.03 V, and high capacity retention of 80 % over 70 cycles in half cells (292 Wh kg−1 in full cells). Crucially, the high Na content is sufficient to provide high energy densities in full cell format. The intergrown nature of the material was confirmed by TEM and SAED analysis, while ex‐situ XRD studies revealed the two phases undergo complementary c‐parameter evolution, reducing overall volume change. These results demonstrate the potential for future commercialisation of bi‐phasic materials utilizing only Earth abundant elements. [ABSTRACT FROM AUTHOR]

Oxygen anion redox offers an effective strategy to enhance the energy density of layered oxide positive electrodes for sodium‐ and lithium‐ion batteries. However, lattice oxygen loss and irreversible structural transformations over the first cycle may result in large voltage hysteresis, thereby impeding practical application. Herein, ribbon superstructure ordering of Li/transition‐metal‐ions was applied to suppress the voltage hysteresis combined with Ti‐substitution to improve the cycling stability for P3‐Na0.67Li0.2Ti0.15Mn0.65O2. When both cation and anion redox reactions are utilized, Na0.67Li0.2Ti0.15Mn0.65O2 delivers a reversible capacity of 172 mA h g−1 after 25 cycles at 10 mA g−1 between 1.6–4.4 V vs. Na+/Na. Ex‐situ X‐ray diffraction data reveal that the ribbon superstructure is retained with negligible unit cell volume expansion/contraction upon sodiation/desodiation. The performance as a positive electrode for Li‐ion batteries was also evaluated and P3‐Na0.67Li0.2Ti0.15Mn0.65O2 delivers a reversible capacity of 180 mA h g−1 after 25 cycles at 10 mA g−1 when cycled vs. Li+/Li between 2.0–4.8 V. [ABSTRACT FROM AUTHOR]

This work investigates the role of crystallization layers' periodicity and thickness on functional response in chemical solution-deposited lead zirconate titanate thin films, with periodic, alternating Zr and Ti gradients normal to the surface of the film. The films were processed with a range of layer periodicities and similar total film thickness, in order to relate the number of layers and compositional oscillations to structural and functional response changes. Trends of increased extrinsic contributions to the dielectric and ferroelectric responses are observed with increasing layer periodicity, but are counterpointed by simultaneous reduction in intrinsic contributions to the same. Transmission electron microscopy reveals inplane crystallographic discontinuity at individual crystallization interfaces. Samples with smaller periodicity, and thus thinner layers, potentially suffer from grain size refinement and subsequent reduction in domain size, thereby limiting extrinsic contributions to the response. The strong compositional oscillations in samples with larger periodicity result in deep fluctuations to the tetragonal side of the phase diagram, potentially reducing intrinsic contributions to the response. Conversely, piezoresponse force microscopy results suggest that large chemical oscillations in samples with larger periodicity also result in closer proximity to the morphotropic phase boundary, as evidenced by local acoustic softening at switching, signaling potential field-induced phase transitions. [ABSTRACT FROM AUTHOR]