Decoding the Atomic-Scale Structural Origin of Large Strain Performance in BNT-6BT Based Relaxor Ferroelectrics.

The relationship between matter properties and their atomic-scale structures is a challenging investigation. For relaxor ferroelectrics, correlating the relaxor mechanisms on the atomic scale to properties is still ambiguous. Here, the correlation between the atomic-scale structure and strain performance of 0.94 Bi0.5Na0.5TiO3-0.06BaTiO3 (94BNT-6BT) and 0.93 Bi0.5Na0.5TiO3-0.06BaTiO3-0.01BaZrO3 (93BNT-6BT-1BZ) is reported. The δTi-Bi/Na displacement vector map based on the annular dark field (ADF) scanning transmission electron microscopy (STEM) image demonstrates the coexistence of tetragonal (T) and rhombohedral (R) phases of the resulting ceramics, and BZ doping increases the proportion of the T phase. Furthermore, the enhanced annular bright field (eABF) STEM image demonstrates that BZ doped ceramics exhibit obvious oxygen octahedral tilt. The oxygen octahedral tilt increased gradually from the domain wall to the inner place of the nanodomain, indicating a regional consistency, which results in enhancement of the relaxor performance and stain property. This study opens exciting opportunities to the design of relaxor ferroelectrics with large strain for high-displacement actuator applications.

Controlled Synthesis of Sub-Millimeter Nonlayered WO2 Nanoplates via a WSe2 -Assisted Method.

2D metal oxides (2DMOs) have stimulated tremendous attention due to their distinct electronic structures and abundant surface chemistry. However, it remains a standing challenge for the synthesis of 2DMOs because of their intrinsic 3D lattice structure and ultrahigh synthesis temperature. Here, a reliable WSe2 -assisted chemical vapor deposition (CVD) strategy to grow nonlayered WO2 nanoplates with tunable thickness and lateral dimension is reported. Optical microscopy and scanning electron microscopy studies demonstrate that the WO2 nanoplates exhibit a well-faceted rhombic geometry with a lateral dimension up to the sub-millimeter level (≈135 µm), which is the largest size of 2DMO single crystals obtained by CVD to date. Scanning transmission electron microscopy studies reveal that the nanoplates are high-quality single crystals. Electrical measurements show the nanoplates exhibit metallic behavior with strong anisotropic resistance, outstanding conductivity of 1.1 × 106  S m-1 , and breakdown current density of 7.1 × 107  A cm-2 . More interestingly, low-temperature magnetotransport studies demonstrate that the nanoplates show a quantum-interference-induced weak-localization effect. The developed WSe2 -assisted strategy for the growth of WO2 nanoplates can enrich the library of 2DMO materials and provide a material platform for other property explorations based on 2D WO2 .

One-Dimensional (NH=CINH3)3PbI5 Perovskite for Ultralow Power Consumption Resistive Memory.

Organic-inorganic hybrid perovskites (OIHPs) have proven to be promising active layers for nonvolatile memories because of their rich abundance in earth, mobile ions, and adjustable dimensions. However, there is a lack of investigation on controllable fabrication and storage properties of one-dimensional (1D) OIHPs. Here, the growth of 1D (NH=CINH3)3PbI5 ((IFA)3PbI5) perovskite and related resistive memory properties are reported. The solution-processed 1D (IFA)3PbI5 crystals are of well-defined monoclinic crystal phase and needle-like shape with the length of about 6 mm. They exhibit a wide bandgap of 3 eV and a high decomposition temperature of 206°C. Moreover, the (IFA)3PbI5 films with good uniformity and crystallization were obtained using a dual solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). To study the intrinsic electric properties of this anisotropic material, we constructed the simplest memory cell composed of only Au/(IFA)3PbI5/ITO, contributing to a high-compacted device with a crossbar array device configuration. The resistive random access memory (ReRAM) devices exhibit bipolar current-voltage (I-V) hysteresis characteristics, showing a record-low power consumption of ~0.2 mW among all OIHP-based memristors. Moreover, our devices own the lowest power consumption and "set" voltage (0.2 V) among the simplest perovskite-based memory devices (inorganic ones are also included), which are no need to require double metal electrodes or any additional insulating layer. They also demonstrate repeatable resistance switching behaviour and excellent retention time. We envision that 1D OIHPs can enrich the low-dimensional hybrid perovskite library and bring new functions to low-power information devices in the fields of memory and other electronics applications.