Cui Yongbao,Yan Tianxiang,Wang Zhaohui,Sun Haochen,Lei Xiuyun,Yan Shiguang,Fang Liang,Liu Laijun
(1 − x )K 0.5 Na 0.5 NbO 3 – x La(Zn 0.5 Zr 0.5 )O 3 [(1 − x )KNN– x LZZ, x = 0.005, 0.010, 0.015, 0.020] ceramics were synthesized to fulfill the application requirement of high-temperature ceramic capacitors. The influence of LZZ content on the phase structure, microstructure morphology, dielectric and conductivity behaviors of this system was conducted. An orthorhombic phase for 0.005 ≤ x ≤ 0.010 and an orthorhombic-tetragonal coexisting phase for 0.015 ≤ x ≤ 0.020 were determined by the X-ray diffraction, Rietveld refinement, and dielectric spectra. The ceramic with x = 0.015 exhibits an ultrahigh and stable permittivity ( ε' ~ 1892, ± 15% variation) and a low dielectric loss (tan δ ≤ 0.05) in a wide temperature region of 82–382 °C owing to the composition heterogeneity-induced shoulder-like peak and diffuse phase transition from tetragonal to cubic. The activation energies from the high-temperature dielectric relaxation and conductivity behaviors initially enhance greatly and then increase slowly, which could be related to the synergy effect of decreased oxygen vacancies and microstructure morphology evolution.
Composites featuring negative permittivity have garnered significant attention for their potential in novel capacitance designs, coil-less electrical inductors, and electromagnetic shielding applications. In this study, we prepared polyvinylidene fluoride (PVDF) matrix composites filled with ZrO 2 /C nanoparticles derived from metal-organic frameworks (MOFs) via a hot-pressing method. With an increase in the ZrO 2 /C content to 30 wt.%, electrical percolation was observed, accompanied by a transition mechanism from hopping conduction to metal-like conduction. This enabled the realization of ZrO 2 /C/PVDF composites with tailorable negative permittivity properties, attributed to the plasmonic oscillation of free electrons in the composites beyond the percolation threshold (30 wt.%). Furthermore, the permittivity transition along to a shift in the electrical behavior of the percolative composites from capacitive to inductive. We explored the regulatory mechanism behind the negative permittivity in this random composite system, and our findings highlight the potential of these tunable negative permittivity media as promising candidates for diverse electromagnetic applications.
Ultrathin 1T@2H-MoS2 films have excellent electronic and optical properties, and are potentially applicable in optics, electronics, energy storage, and sensing technology. However, identification of an efficient method to produce 1T@2H-MoS2 films with controllable thickness is challenging. This study describes the rapid synthesis (5–10 min) of 1T@2H-MoS2 thin films on Si/SiO2 substrates by a novel pulsed laser irradiation method. We verify the photodecomposition reaction model by measuring the UV-Vis absorption spectra of the reactants. The thickness of the synthesized MoS2 film can be controlled by adjusting the concentration of the precursor. Structural characterization confirms that both the 1T and 2H phases exist in the MoS2 film. The 1T phase enhances the conductive behavior of the MoS2 film and induces magnetism. Furthermore, pure 1T-MoS2 can be separated selectively from the MoS2 film under specific operating conditions using pulsed laser-induced synthesis. This approach is suitable for the synthesis of films of MoS2 and other 2D materials, including 1T phase-pure films.
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