The Aurivillius compound Pb x Bi 6− x Fe 0.5 Co 0.5 Ti 4 O 18 thin films were prepared via chemical solution deposition method and the influence of Pb 2+ ions doping on the structure, ferroelectric and leakage properties were studied. With the increasing concentration of Pb 2+ ions, the lattice distortion is increased and the growth of the films along ab plane is promoted. The calculation results show that the internal stress of the films increases with the increase of Pb 2+ concentration. For the samples with low Pb 2+ doping concentration ( x < 0.6), the leakage current densities are also decreased, which can be attributed to the decrease in oxygen vacancy concentration. Due to the enhanced lattice distortion and decreased leakage current densities, the ferroelectric properties are improved. The film with x = 0.2 has a high saturation polarization of 42.3 µC/cm 2 . According to the fitting results, the leakage conduction mechanism is attributed to the combined effect of space-charge-limited conduction mechanism and ionic conduction mechanisms.
In this work, non-stoichiometric Li 2(1+ x ) Mg 3 Ti 4 O 12 (L x MTO, x = 0.00–0.05) ceramics with excess lithium were prepared through a simple reaction sintering route to suppress lithium volatilization. According to the characterization of the phase composition and microscopic morphology of the pellets, single-phase L x MTO ceramics with a good microstructure were obtained. Excess lithium effectively inhibited the volatilization and optimized the morphology of the ceramics. A trend in relative density with an initial increase followed by a steep decrease was a predominant observation with the change in dielectric properties. The permittivity of the samples was dominated by the relative density and distortion of the [TiO 6 ] octahedron structure caused by Li + . The dielectric loss primarily originated from the refraction loss and scattering generated by pores, and the grain boundaries also contributed to the loss in the quality factor. Ultimately, at 1220°C, the Li 2.08 Mg 3 Ti 4 O 12 ceramics exhibited excellent microwave dielectric properties: ε r = 17.83, Q × f = 69,823 GHz and τ f = −18.19 ppm/°C.
Ranxi Liang,Chaozhu Shu,Anjun Hu,Minglu Li,Zhiqun Ran,Ruixin Zheng,Jianping Long
The sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics greatly limit the development of lithium-oxygen (Li-O 2 ) batteries. Therefore, developing efficient electrocatalysts with high stability to boost oxygen involved reactions is particularly important for promoting the application of Li-O 2 batteries. Here, CoSe 2 @NiSe 2 heterostructure with distinct heterogeneous interfaces was fabricated via deliberate interface engineering. The formation of heterogeneous interface promotes local fine atomic array distortion that can act as an additional active site of ORR/OER. In addition, CoSe 2 @NiSe 2 with a distinct heterogeneous interface is favorable for the formation of built-in electric field during charging/discharging to enable electrodes with fast electrical transfer rates and reaction kinetics. Synergistically, the additional active sites brought by the fine atomic array distortion are highly conducive to the reversible formation and decomposition of the product. Undoubtedly, batteries with CoSe 2 @NiSe 2 exhibit excellent discharge/charge capacity (3530.1 mA h g −1 and 3485.6 mA h g −1 ), low overpotential (1.21 V) and excellent electrochemical stability for over 1200 h.
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