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Information processing and memorizing in the brain take place in a neural network consisting of neurons connected with each other by synapses. Meanwhile, the neural network is immersed in a common electrochemical environment with global parameters regulating the overall functions, which is barely discussed in neuromorphic devices. In this study, organic/inorganic hybrid transistors with sodium alginate as the gate dielectric layer and indium tin oxide as the channel were successfully prepared. We have not only simulated the basic properties of synapses in a single device, but, on top of that, also simulated the global regulation of information processing in the brain due to the incorporation of global grids, achieving excitatory and inhibitory synaptic weight. Moreover, the construction of a 3 × 3 synaptic array enables image learning and memorizing functions. These results demonstrate the significant advantages of electrolyte-gated transistors in enabling complex neural network connectivity and offer a promising opportunity for future artificial synapses. [ABSTRACT FROM AUTHOR]

The influence of electrodes on antiferroelectricity and fatigue endurance of 15 nm thick Hf0.2Zr0.8O2 thin films has been studied by a metal–antiferroelectric–metal capacitor structure using TiN and W as electrodes. The W|Hf0.2Zr0.8O2|W capacitor shows significantly enhanced antiferroelectricity and better endurance compared to the capacitor using TiN as the electrode. Assisted by grazing incidence x-ray diffraction and scanning transmission electron microscopy, the different electrical properties are discussed based on the contents of different phases and the diffusion of oxygen from the thin film into electrodes. [ABSTRACT FROM AUTHOR]

When embedded within a ferroelectric host matrix, rare-earth ions and their photoluminescence (PL) provide an original all-optical light probe for temperature, electric field and mechanical stimulus. However, a clear and global view of how PL is affected by the phase transitions that are inherent to ferroelectric materials is still lacking. Here, using an Er-doped BaTiO3 model ferroelectric material, we demonstrate that the PL of the green emission bands resulting from a 488 nm light excitation exhibit changes at the critical ferroelectric transitions. The transition temperatures also have a signature on the absolute temperature sensitivity we extracted from the ratio of the two main green emission bands. Furthermore, we demonstrate that the sub-peaks related to the lifting of degeneracy by the crystal field also contain information on the phase transitions. We propose that the intensity ratio and the wavelength position difference of some of these sub-peaks can be used as order parameters to describe the phase transitions. We hope our results will help better understand the link between light emission features and local polar and macroscopic structures. [ABSTRACT FROM AUTHOR]

Multiferroic materials have attracted significant research attention due to their technological potential for applications as multifunctional devices. The scarcity of single-phase multiferroics and their low inherent coupling between multiferroic order parameters above room temperature pose a challenge to their further applications. We propose a 3BiFeO3/7BaTiO3 perovskite–perovskite composite that combines ferroelectricity and ferromagnetism. We demonstrate that the sintering temperature can tailor the ferroelectricity and ferromagnetism of the composites. The multiferroicity can be achieved at a low sintering temperature in the composite-like structure ceramics, and its multiferroic properties, especially the ferromagnetism, are superior to those of solid solutions. We also investigate the dynamic evolution of multiferroicity with sintering temperature. We adopt a nano–micro strategy to construct a composite-like microstructure, which results in optimized ferroelectric (1.62 μC cm−2) and ferromagnetic (0.16 emu/g) characteristics at a sintering temperature of 750 °C. We also found experimental evidence of the competition between antiferromagnetic and ferromagnetic interactions in the transition metal cation sublattice. Multiferroic BiFeO3/BaTiO3 composites with combined ferroelectric and ferromagnetic properties have significant potential for various applications. [ABSTRACT FROM AUTHOR]

The combination of significant polarization and large light absorption is a challenge in ferroelectric materials. Here we report the optical absorption of BaTiO3 codoped with trivalent and pentavalent transition metal ions replacing the Ti4+ cation, i.e., BaTi1−x(X1/2Y1/2)xO3 (X = Sc, Mn, Fe, Co; Y = Nb, Ta; with x = 0.075). We investigated the optical absorption behavior as a function of different pairs of co-dopants as well as physical properties such as ferroelectricity and piezoelectricity. X-Ray diffraction and Raman spectroscopy measurements show that the tetragonality and polar coherence length decrease after co-doping, which affects the ferroelectric properties. It was found that the onset of absorption can decrease down to 1.5 eV, especially for the (Co3+, Nb5+) co-doped samples, which simultaneously exhibit higher polarization than with the other co-doped ions. The measured photoconductivity confirms that the (Co3+, Nb5+) doping has higher absorption than others. Our density functional theory calculations show that codoping inserts intragap levels which are responsible for lowering the energy of optical absorption, which is in full agreement with our experimental observations. This work opens new perspectives for the use of ferroelectrics in optoelectronic devices. [ABSTRACT FROM AUTHOR]

Titanium dioxide (TiO2)–zinc tungstate (ZnWO4) nanocomposite powder was prepared by a sol–gel procedure. The X-ray diffraction pattern (XRD) of the nanocomposite indicates that the crystallinity of TiO2 is reduced by coupling with ZnWO4. High resolution microscopic observation of the nanocomposite reveals the intimate contacts formed between the TiO2–ZnWO4 interfaces. The composite's structure slightly reduces the aggregation of the unmixed TiO2 and ZnWO4, leading to a larger surface area. The photoluminescence (PL) spectrum of the nanocomposite exhibits a prominent broad emission band centered at about 470 nm, compared with that of the pure ZnWO4. Gaussian fitting of the PL peak of the nanocomposite suggests a reduced number of oxygen defects on the ZnWO4 surface. This is further confirmed by X-ray photoelectron spectroscopy (XPS) analysis of the nanocomposite, and the number of oxygen defects on the surface of TiO2 is demonstrated to be increased by coupling with ZnWO4. The photocatalytic activity of the nanocomposite was evaluated by degrading methyl orange under UV light irradiation. The results showed that the photocatalytic performance of TiO2 is much improved through coupling with ZnWO4. [ABSTRACT FROM AUTHOR]

Sm3+ doped Sr1.90Ca0.15Na0.9Nb5O15 (SCNN: xSm3+) multifunctional ferroelectric ceramics with pure tetragonal tungsten bronze phase were synthesized via the conventional solid-state reaction method. The dielectric, ferroelectric characteristics and luminescent behaviors were systematically studied. The electrical properties suggested that a moderate Sm3+ doping could enhance the electrical performances. The orange-reddish emission originated from the transition of 4G5/2 → 6H7/2, 4G5/2 → 6H5/2 and 4G5/2 → 6H9/2 was observed under excitation wave of 406 nm. The strongest emission intensities were obtained at the Sm3+ doping content of 0.010. The degree of thermal quenching for the composition with x = 0.010 was relatively lower and the normalized emission intensity continued still 80% from room temperature to 150 °C. Besides, the transmittance in visible spectra of the SCNN: xSm3+ ceramics could be improved obviously, which was up to 50% at the doping amount of 0.010. These results show that the SCNN: xSm3+ multifunctional ferroelectric niobates have promising potential in electric-optical devices. [ABSTRACT FROM AUTHOR]