The relationship among dielectric anomaly, ferroelectric response, defects, and microstructures was established for (KNa)LiNbSbO (x = 0.04, 0.00, -0.02, -0.04 and -0.08) ceramics. For x = -0.02 and -0.04, larger coercive fields and lower remnant polarizations were obtained; besides, an additional dielectric relaxation behavior was observed with the activation energy E being about 2.19 eV and 1.92 eV, respectively. Furthermore, the grain and grain boundary contributions to the capacitance were separated using impedance spectroscopy, which, combined with back-scattering characterization, firmly indicates the core-shell structure of K-deficient samples (x = -0.02 and -0.04). Unlike the cores, the shells possess a large amount of K vacancies (). This work paves a way for regulating the fine structure and more on the electrical properties of KNN-based materials.

Resistive switching behaviors of SnO2 films are largely improved by Cu acceptor doping. At a suitable Cu2+ concentration, a high ON/OFF resistance ratio (104), good endurance (104) and long retention (104 s) are achieved in the Cu/SnO2:Cu/Pt sandwich structure with the modulation of carriers and oxygen vacancies. As a memristor, the resistive switching can be triggered by one pulse or a train of pulses, and the latter mode could simulate the long-term potentiation of biological synapses. Moreover, the multi-resistance states during the reset process demonstrate a combination of abrupt and incremental resistive switching. The peculiar conductive behavior of the devices is considered to result from the cooperation of conductive filaments and Schottky barrier, with the oxygen vacancies serving as the bridge. These studies are significant for higher density storage and cognitive computing in future.

The magnetic and magnetodielectric (MD) properties of nanobased Bi2Fe4O9 are investigated. 2 μm  ×  2 μm  ×  300 nm nano-crystals exhibit an anti-ferromagnetic (AFM) transition at 235 K and a weak ferromagnetism in the temperature range of 10–310 K, shown by the magnetic hysteresis loops. The samples show a large MD effect with Δε/ε being about  −13% at 50 K and 0.45 T, as well as an anomaly of MD effect that increases with increasing magnetic field (H). This large MD effect indicates a strong coupling between the magnetic and dielectric properties in Bi2Fe4O9. Our studies provide strong evidence that both the AFM ordering and ferromagnetism contribute to the MD effects.

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