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Numerous studies have shown that ceramic materials with high dielectric constants and low dielectric losses can be obtained using donor–acceptor-doped TiO2. In this study, (La + Nb)-co-doped TiO2 [(La0.5Nb0.5)xTi1−x O2 x-LNTO] ceramic powders were prepared using the sol–gel method. XRD demonstrates that LNTO is a rutile phase, and the lattice parameters change after doping, while X-ray photoelectron spectroscopy explains the doping mechanism, with doping of TiO2 producing oxygen vacancies and Ti3+, which form defective dipoles with the dopant ions to increase the dielectric constant of the material. The dielectric properties were investigated by physically co-blending x-LNTO/polyvinylidene difluoride (PVDF) composites. Compared with the TiO2/PVDF composite, the dielectric properties of the x-LNTO/PVDF composite were more excellent. The dielectric constant of 5-LNTO/PVDF reached 36.96, which was higher than that of the TiO2/PVDF composite (19.49) at a filler addition of 60 wt% and a frequency of 1 kHz.

In this work, strontium titanate (STO) was coated on the surface of carbon nanotubes (MWCNTs) through a sol–gel method to form a core–shell structure hybrid powder (STO@MWCNTs). This powder was then added to polydimethylsiloxane to prepare a flexible high-K composite. As coating, STO effectively prevents the overlap and agglomeration of MWCNTs, thereby passivating the percolation threshold of the composite. STO increases the dielectric properties of the composite as a high dielectric ceramic. Under a low filler loading amount of 11 wt%, the dielectric constant and dielectric loss of the composite are 53 and 0.1, respectively. In addition, the composite can still maintain superior breakdown strength and mechanical properties, given the relatively low filler concentration. The enhanced dielectric properties, breakdown strength, and tensile strength make the composite suitable for application as dielectric material in flexible and stretchable energy storage equipment.

According to theoretical studies on ceramic/polymer composite dielectrics, the maximum achievable dielectric constant is observed in composites with a parallel structure connecting the ceramic and polymer phases. However, the practical preparation of parallel-structured composites poses significant challenges. Here, aimed at the theoretical model, we prepared a parallel-structured BaTiO3 (BT) skeleton through bidirectional freezing, and further prepared a parallel-structured BaTiO3/epoxy (BT/EP) composite through vacuum impregnation. When the electric field is completely parallel to the interfaces between BT and EP phases, the composites basically realize the ideal parallel structure and exhibit excellent dielectric properties. For example, the composite with 59 vol% BT content has an ultra-high dielectric constant of 2017 and shows a low loss of <0.02 at 1 kHz. Even at a low BT content of 18 vol%, the dielectric constant of the parallel-structured composite is still as high as 489 at 1 kHz. Based on the ultra-high dielectric constant of the parallel-structured composites, a high polarization intensity of 24.8 μC cm−2 and a discharge energy density of 13.4 × 10−2 J cm−3 are achieved at a low electric field of 4 kV mm−1. Experiments and simulations demonstrated that the parallel arrangement along the direction of the electric field and the connectivity of the ceramic fillers are the key factors to realize the parallel structure. This work achieved the parallel structure described by the theoretical model and further clarified the relationship between the structure and dielectric properties of the composites. [ABSTRACT FROM AUTHOR]

With the rapid development of science and technology, it is urgent to develop the extreme condition-resistance and multifunctionality of sensors to broaden their application scenarios. Here, an extreme condition-resistant superelastic silica nanofiber (SNF)/MXene composite aerogel is fabricated by an ice-templating assembly strategy. The hierarchical three-dimensional cellular structure composed of conductive two-dimensional MXene nanosheets as a framework and flexible one-dimensional SNFs as a scaffold endows the composite aerogel with excellent mechanical and piezoresistive properties at an ultralow density of 9 mg cm−3. The assembled aerogel sensor shows a high sensitivity (−0.33 kPa−1), ultralow detection limit (0.01 kPa), rapid response/recover time (72/99 ms), large workable strain range (1–80%), and good stability (>5000 cycles), capable of detecting various human motions in real time, whether faint pulse beating or strenuous running. More importantly, the composite aerogel still maintains excellent mechanical and piezoresistive stability (>1000 cycles) after high-temperature baking (600 °C) or at ultralow temperature (−130 °C), even in liquid nitrogen (−196 °C). Furthermore, the outstanding thermal insulation performance (24.7 mW m−1 K−1) and exceptional low-voltage driven Joule heating performance (126.5 °C at 5 V) of the composite aerogel are presented simultaneously in a dual-mode thermal management device integrating heat generation and insulation. Based on these characteristics, a multifunctional aerogel sensor that can be used for synchronous sensing and thermal management is demonstrated for the first time. This work offers a novel insight into the development of multifunctional aerogel sensors and greatly broadens the application scenarios of wearable devices. [ABSTRACT FROM AUTHOR]

Using high-dielectric inorganic ceramics as fillers can effectively increase the dielectric constant of polymer-based composites. However, a high percentage of fillers will inevitably lead to a decrease in the mechanical toughness of the composite materials. By introducing high aspect ratio copper calcium titanate (CaCu 3 Ti 4 O 12 ) nanowires (CCTO NWs) and graphene as fillers, the ternary poly(vinylidene fluoride) (PVDF)-based composites (CCTO NWs-graphene)/PVDF with a significant one-dimensional orientation structure were prepared by hot stretching. CCTO NWs and graphene are arranged in a directional manner to form a large number of microcapacitor structures, which significantly improves the dielectric constant of the composites. When the ratio of CCTO NWs and graphene is 0.2 and 0.02, the oriented composites have the highest dielectric constant, which is 19.3% higher than the random composites, respectively. Numerical simulations reveal that the introduction of graphene and the construction of the one-dimensional oriented microstructure have a positive effect on improving the dielectric properties of the composites. This study provides a strategy to improve the dielectric properties of composite materials by structural design without changing the filler content, which has broad application prospects in the field of electronic devices., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)