Porous organic cages (POCs) have emerged as a new sub-class of porous materials that stand out by virtue of their tunability, modularity, and processibility. Similar to other porous materials such...

Protonic ceramic fuel cells (PCFCs) are attractive energy conversion devices for intermediate-temperature operation (400-600 °C), however widespread application of PCFCs relies on the development of new high-performance electrode materials. Here...

Mixed ionic–electronic conductors (MIECs) that display high oxide ion conductivity (σo) and electronic conductivity (σe) constitute an important family of electrocatalysts for a variety of applications including fuel cells and oxygen separation membranes. Often MIECs exhibit sufficient σe but inadequate σo. It has been a long‐standing challenge to develop MIECs with both high σo and stability under device operation conditions. For example, the well‐known perovskite oxide Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) exhibits exceptional σo and electrocatalytic activity. The reactivity of BSCF with CO2, however, limits its use in practical applications. Here, the perovskite oxide Bi0.15Sr0.85Co0.8Fe0.2O3−δ (BiSCF) is shown to exhibit not only exceptional bulk transport properties, with a σo among the highest for known MIECs, but also high CO2 tolerance. When used as an oxygen separation membrane, BiSCF displays high oxygen permeability comparable to that of BSCF and much higher stability under CO2. The combination of high oxide transport properties and CO2 tolerance in a single‐phase MIEC gives BiSCF a significant advantage over existing MIECs for practical applications.

In hybrid-doped BaTiO3 ceramics, acceptor (A3+) with higher ER tends to form defect pairs with donors (D5+ or D3+).

The morphotropic phase boundary (MPB) of PbMg1/3Nb2/3O3-xPbTiO3 (PMN-xPT) and its derivatives has been reported to exhibit a giant piezoelectric coefficient (d33). Hence, it is essential to understand the origin of excellent piezoelectric properties. In the present work, we observed that the cubic–tetragonal–rhombohedral triple point in the phase diagram of the PMN-xPT system is itself a critical point. The criticality of the triple point is evidenced by the nearly zero transition thermal hysteresis, the maximized dielectric permittivity, and the largest degree of elastic softening. The Landau modeling calculations reveal that such a critical triple point exhibits infinitely high piezoelectricity, which explains the origin of the giant piezoelectricity of the PMN-xPT system. This work illustrates that the near-criticality of the MPB composition is inherited from the criticality of the triple point. This study would stimulate work on searching materials with high piezoelectricity by designing a critical triple point.

Performance durability is one of the essential requirements for solid oxide fuel cell materials operating in the intermediate temperature range (500–700 °C). The trade‐off between desirable catalytic activity and long‐term stability challenges the development and commercialization of electrode materials. Here an oxygen cathode material, Ba0.5Sr0.5(Co0.7Fe0.3)0.69−xMgxW0.31O3−δ (BSCFW‐xMg), that exhibits excellent electrocatalytic performance through the addition of an optimized amount of Mg to the self‐assembled nanocomposite Ba0.5Sr0.5(Co0.7Fe0.3)0.69W0.31O3−δ (BSCFW) by simple solid‐state reaction is reported. Distinct from the bulk and surface approaches to introduce vacancies and defects in materials design, here the Mg2+ ions concentrate at the single perovskite/double perovskite interface of BSCFW with dislocations and Mg2+‐rich nanolayers, resulting in stressed and compositionally inhomogeneous interface regions. The interfacial chemistry within these nanocomposites provides an additional degree of freedom to enable performance optimization over single phase materials and promotes the durability of alkaline‐earth based fuel cell materials.