Accurately determining local polarization at atomic resolution can unveil the mechanisms by which static and dynamical behaviors of the polarization occur, including domain wall motion, defect interaction, and switching mechanisms, advancing us toward the better control of polarized states in materials. In this work, we explore the potential of atomic-resolution scanning transmission electron microscopy to measure the projected local polarization at the unit cell length scale. ZnO and PbMg1/3Nb2/3O3 are selected as case studies, to identify microscope parameters that can significantly affect the accuracy of the measured projected polarization vector. Different STEM imaging modalities are used to determine the location of the atomic columns, which, when combined with the Born effective charges, allows for the calculation of local polarization. Our results indicate that differentiated differential phase contrast (dDPC) imaging enhances the accuracy of measuring local polarization relative to other imaging modalities, such as annular bright-field or integrated-DPC imaging. For instance, under certain experimental conditions, the projected spontaneous polarization for ZnO can be calculated with 1.4% error from the theoretical value. Furthermore, we quantify the influence of sample thickness, probe defocus, and crystal mis-tilt on the relative errors of the calculated polarization.

This manuscript describes, defines, and discusses the process of cold sintering, which can consolidate a broad set of inorganic powders between room temperature and 300 °C using a standard uniaxial press and die. This temperature range is well below that needed for appreciable bulk diffusion, indicating immediately the distinction from the well-known and thermally driven analogue, allowing for an unconventional method for densifying these inorganic powders. Sections of this report highlight the general background and history of cold sintering, the current set of known compositions that exhibit compatibility with this process, the basic experimental techniques, the current understanding of physical mechanisms necessary for densification, and finally opportunities and challenges to expand the method more generically to other systems. The newness of this approach and the potential for revolutionary impact on traditional methods of powder-based processing warrants this discussion despite a nascent understanding of the operative mechanisms.

Why did the Ghanaian state go to such extraordinary lengths to facilitate the reliable broadcast of the World Cup in 2014? During a period of frequent power outages, Ghana swapped power with regional neighbours and directed major domestic industries to reduce production in order to allow Ghanaians to watch their national soccer team compete in the World Cup. This paper investigates the politics of the public service provision of electricity in Ghana. We focus on the short-term crisis during the 2014 World Cup to reveal the citizens' and politicians' expectations about electricity as a public good. Drawing on an analysis of archival documents, Ghanaian newspapers, and interviews with government, business, and NGO officials in the energy sector, we argue that the Ghanaian state historically has created the expectation of electricity as a right of national citizenship and explore how this intersects with competitive party politics today.

The refractory nature of BaTiO3 leads to limited densification and grain growth for films processed at low temperatures and a modest nonlinear dielectric response due to a marked sensitivity to physical scale and material quality. Adding liquid-forming sintering aids, common in bulk ceramics, to thin films enhances mass transport, leading to enhanced grain growth at lower temperatures. This work explores the effectiveness of a sputtered CuO buffer layer with BaO–B2O3 (BBO) fluxes to engineer the microstructure of BaTiO3 films. Grain size and homogeneity increase in the presence of even a ∼1 nm CuO layer. In general, grain size increases from 75 to 370 nm with an addition of 2.2% BBO and 8 nm CuO. Room temperature capacitance in fluxed films increases by a factor of 5 over pure films, and ferroelectric phase transitions are clearly observable in dielectric measurements. CuO–BBO proves effective on (0001) Al2O3 and (100) MgO substrates, although all microstructures are notably finer for the latter.