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The double peroskite Lu 2 NiMnO 6 was synthesized by a facile hydrothermal method. X-ray power diffraction (XRD) analysis shows it adopts monoclinic structure with space group P2 1 /n , indicating an ordered arrangement at B sites. Valence states analysis done by XPS shows Ni 2+ /Mn 4+ configuration. Raman spectrum reveals an ordered structure in the sample, in agreement with the XRD results. The degree of ordering was greatly enhanced after the sample was annealed at 873 K. Magnetism of the as-grown and annealed samples was analyzed using DC and AC magnetization, as well as Magnetization-Hysteresis. Dielectric anomaly independent on frequency was observed close to the magnetic ordering temperature, indicating the possibility of ferroelectricity and further magnetoelectric coupling. [ABSTRACT FROM AUTHOR]

The perovskite orthoferrite SmFeO 3 was synthesized by the hydrothermal method. The Néel temperature of this material was found to be 655 K by temperature-dependent magnetization measurements. Magnetic field-dependent magnetization of the material at 300 K revealed typical weak ferromagnetic behaviour. Dielectric analysis showed a ferroelectric phase transition at 480 K. The structural and magnetic properties of SmFeO 3 were also characterized using Mössbauer spectra, which also confirmed this structural transition. The remanent polarization determined by the positive-up-negative-down (PUND) method was approximately 0.012 μC/cm 2 at 173 K. Therefore, the results presented here indicate that SmFeO 3 is multiferroic at temperatures above room temperature. Our analysis shows that the material's non-centrosymmetric Pna2 1 structure is likely to be responsible for the ferroelectricy in SmFeO 3 rather than the Pbnm structure or the magnetic structure. [ABSTRACT FROM AUTHOR]

Flexible piezoelectric nanogenerators (PENG) have attracted wide attention because of their great potential in solving the power supply problem of wearable electronic devices. In order to expand the applications of PENG, high quality (Na 0.5 Bi 0.5)TiO 3 -0.06BaTiO 3 (NBT-0.06BT: x Er3+) nanofibers doped with different Er3+ concentrations were prepared by the gel-sol electrostatic spinning method. The morphology and phase structure of the prepared nanofibers were characterized. Dense nanofibers with good crystallization have been obtained. The local ferroelectric properties of the nanofibers were characterized by PFM. It is found the prepared nanofibers have a strong upconversion (UC) photoluminescence (PL) property. Utilizing the fluorescence intensity ratio (FIR) technique, the temperature sensing properties of the nanofibers has been investigated, showing a maximum sensitivity of 0.0043 K−1. Finally, the flexible PENG was prepared by encapsulating NBT-0.06BT:0.01Er3+ nanofibers, interdigital electrode and PDMS. The maximum voltage output of PENG is 97 V. The present investigation integrates the luminescence characteristics and electrical properties of nanofibers into the flexible PENG, which may greatly expand its application field. • NBT-0.06BT: x Er3+ nanofibers with high quality have been successfully prepared. • NBT-0.06BT: x Er3+ nanofibers have excellent temperature sensing properties. • The present PENG has a potential application in optics. • The output voltage of the PENG reaches a high value of 97 V. [ABSTRACT FROM AUTHOR]

In polycrystalline ceramics, charge trapping property has important impact on the dielectric breakdown strength (DBS). In this work, alumina ceramics with Ca 9 Al(PO 4) 7 (CAP) as the second crystalline phase were synthesized using coarse alumina as main raw materials, and the CAP crystal being dendritic or granular depends on the mass ratio of calcium phosphate to kaolin in the raw material composition. Microstructure and impedance spectrum indicated that dendritic CAP with typical fractal features greatly increases the charge trapping sites and charge spreading barrier. The AC DBS of ceramics with 70 wt% alumina and fractal dendritic CAP achieved a competitive value of 16.1 kV/mm. The results indicate that growing fractal dendritic CAP between the main crystalline grains is a very feasible way to enhance the DBS of alumina ceramic. • Dendritic fractal Ca 9 Al(PO 4) 7 can be obtained simply and stably. • Dendritic Ca 9 Al(PO 4) 7 greatly increases the charge-trapping property. • The effects of the morphology and content of the second phase on the breakdown dielectric strength were investigated. • An effective and low-cost way was provided to enhance the dielectric breakdown strength of alumina ceramics. [ABSTRACT FROM AUTHOR]

The NaCl:XEu (with X = 0.0, 0.002, 0.004, 0.006, 0.008, 0.01, 0.02 and 0.04) crystals have been grown in air by the melt (Czochralski) method and have investigated the Eu concentration dependence of the structural, physical and optical (optical absorption, photoluminescence and thermo-luminescence) properties by using the available characterization techniques. X-ray diffraction and photoluminescence (PL) studies on the doped crystals have confirmed the presence of Eu ions (existing as Eu2+ and Eu3+ ions) in the NaCl crystal matrix. Hardness measurement has shown that the Eu doped crystals belong to the hard material category and the hardness and elastic stiffness constant decrease with the load increase and increase with the Eu concentration increase. Optical absorption spectra have revealed that five new peaks appear on doping with Eu ions. PL spectra have shown increase in emission intensity with the increase in concentration of Eu2+ and Eu3+ ions. Thermo-luminescence (TL) glow curves exhibit two peaks at ~103.7 and ~199.9 ℃. The TL peak intensities observed for the Eu doped NaCl crystals are much larger than the pure NaCl crystal. NaCl:XEu crystal with X = 0.008 has been found to possess the optimal luminous (both PL and TL) properties. The TL parameters calculated prove that the activation energy (E) values vary with the Eu concentration and the trap concentration (n 0) values of the high temperature peak are larger than that for the low temperature peak. • Large size NaCl:XEu crystals were grown in air by the Czochralski method. • The hardness of the crystals decrease with the increase in load and increase with the increase in Eu concentration. • The emission intensity of the Eu ions increase with the increase in Eu concentration and attain maximum at X = 0.008. [ABSTRACT FROM AUTHOR]

• The modification strategy with PDA@nano-TiO 2 was designed to enhance electrochemical performance of spinel LNMO. • PDA@TiO 2 -LNMO cathode showed high reversible capacities and good capacity retention. • The excellent performance was attributed to PDA@nano-TiO2 as protective layer and good conductor for Li+ diffusion. The surface modification of LiNi 0.5 Mn 1.5 O 4 cathode material with PDA@TiO 2 enable it gain the high reversible capacities and good capacity retention. [Display omitted] Improving the cycling performance without sacrificing its capacity is challenging for high-voltage LiNi 0.5 Mn 1.5 O 4 cathode due to the trade-off nature among the key properties. A self-polymerization process of dopamine was utilized to grow polydopamine (PDA)-nano titanium dioxide assembly. PDA@TiO 2 composite was demonstrated to be integrated with the particles of high-voltage spinel LiNi 0.5 Mn 1.5 O 4 cathodes via wet chemical method. PDA@TiO 2 decorated LNMO improved the long-term cycling performance and rate capability by suppressing detrimental side reactions in balancing the interfacial stability and Li+ diffusion kinetics of LNMO and consequently providing efficient conductive pathways. As a result, 2% PDA@TiO 2 modified LNMO cathode exhibited the high reversible capacity of 117 mAh g−1 after 1000 cycles with good capacity retention of 90.7% at 1 C, and superior rate capability (78.5 mAh g−1 at 5 C) at room temperature. Remarkably, a significant improvement in cycling stability at an elevated temperature (50 °C) was obtained for the PDA@TiO 2 -LNMO composite, giving a capacity retention of 93% after 100 cycles at 1 C. The mechanism of performance improvement could be attributed to the maintenance of the structural stability of LNMO cathode materials and the enhanced kinetics of the remarkable lithium-ion diffusion through the protective effect of PDA@TiO 2 decorating. [ABSTRACT FROM AUTHOR]

Pt-based catalysts are widely used in polymer electrolyte fuel cells. However, it still exists tremendous challenge on improving the activity and durability of electrocatalysts. Herein, Pt nanoparticles (NPs) are supported on the dispersed MoO 3 -modified carbon nanotubes (CNTs) via an atomic layer deposition (ALD) technology. In the resulting Pt-MoO 3 /CNT-ALD, Pt NPs are selectively anchored on the interface of MoO 3 and CNTs to increase the Pt-O bonds and strengthen the metal-metal oxide interaction (MMOI). The regulated electronic structure of Pt can remarkably enhance the intrinsic catalytic activity. For methanol oxidation reaction, Pt-MoO 3 /CNT-ALD exhibits high activity with a mass activity of 1221.1 mA·mg Pt −1 at 0.9 V which represents a 4.2-fold improvement over the corresponding activities of commercial Pt/C. And for oxygen reduction reaction, it shows the onset potential and half potential of 1.04 V and 0.87 V, respectively. Most importantly, Pt-MoO 3 /CNT-ALD exhibits excellent long-term stability without distinct degradation (98.9% retention of electrochemical surface area and 92.4% retention of mass activity) after 10,000 cycles. In single cell test, the maximum power density and durability of the Pt-MoO 3 /CNT-ALD is achieved to be 589 mW·cm−2 and 94.8% retention after 3000 cycles. The Pt-MoO 3 /CNT-ALD with high activity and durability is attributed to the increased Pt-O bonds, optimized electronic structure and strengthened MMOI. A strategy in this work is approved to facilitate the development of high-performance Pt-based electrocatalysts. [Display omitted] • The prepared Pt-MoO3/CNT-ALD electrocatalyst shows highly dispersed structure. • The Pt-O bond attaches Pt nanoparticles on the surface of carbon support. • Pt-MoO3/CNT-ALD exhibits optimal activity and durability in MOR and ORR. • The improved performance should be attributed to the ternary synergy of Pt, MoO3 and CNT. [ABSTRACT FROM AUTHOR]

A series of Ca-doped yttrium iron garnet ceramics (Y 3- x Ca x Fe 5 O 12 (x = 0, 0.05, 0.1, 0.15, 0.2)) were prepared by the solid state method. The structure, morphology, valence fluctuation, thermal analysis, magnetization, magnetodielectric and Mössbauer spectrum of Y 3- x Ca x Fe 5 O 12 ceramics were systematically studied. All of the samples crystalized as single phase of garnet structure with the grain sizes of 2–3 μm. The temperature dependent percentage weight loss and heat flow were investigated by thermogravimetric (TG) and differential scanning caborimetry (DSC). The structure of Y 3- x Ca x Fe 5 O 12 ceramics was studied by XRD, Raman and Infrared (IR) spectra. The results indicated that Ca2+ substitution leads to lattice expansion and presence of Ca–O octahedron, which causes the concentration of Fe2+ decrease and Fe4+ increase. As a result, the saturation magnetization first increases and then decreases with the increase of Ca concentration. A six lines asymmetry of magnetic components were observed in Mössbauer spectrum, which was fitted by two hyperfine magnetic sextets corresponding to tetrahedral and octahedral sites, respectively. With the increase of Ca concentration, the intrinsic magnetodielectric (MD) effect disappears completely due to the dramatic decrease of Fe2+-Fe3+ dipoles. Fe3+-Fe4+ dipoles do not contribute to the MD properties of Y 3- x Ca x Fe 5 O 12 ceramics due to the lack of the defects such as electrons or holes being used as media. • Ca2+ doping in YIG ceramics results in the nonmonotonic variation of its saturation magnetization. • Intrinsic MD effect are observed at room temperature and its value decreases with the increase of Ca2+ doping. • The decrease of Fe2+-Fe3+ dipoles results in the gradually decrease and ultimate vanishing of the MD effect. [ABSTRACT FROM AUTHOR]