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This study examines the low‐loss and temperature‐stable Na2O–Ln2O3–MoO3–TiO2 (Ln = Nd, La and Ce) system, synthesized via a solid‐state process at low‐sintering temperatures ranging from 840°C to 900°C The structure, microstructure and microwave properties of the Na0.5Ln0.5MoO4–TiO2 (Ln = Nd, La and Ce) ceramics as a function of the sintering temperature were studied. The results of XRD patterns and microstructure characterization showed that the main phase in compositions belong to tetragonal scheelite and tetragonal structure. The ceramic composition Na0.5Ln0.5MoO4–TiO2 (Ln = Nd, La and Ce), sintered at 840°C–900°C for 2 hours, demonstrated excellent microwave dielectric properties, exhibiting relative dielectric constant (εr) of 13.9–14.4, Q × f value of about 31 100 (at 9.66 GHz) – 48 600 GHz (at 9.33 GHz), and temperature coefficient of –8.1 to –1 ppm/°C. Our work designs temperature‐stable microwave dielectric ceramics with low‐sintering temperature for LTCC technology applications. [ABSTRACT FROM AUTHOR]

In the present work, five compositions in the BaO–MgO–SiO2 ternary system were chosen, and ceramics were prepared using the solid‐state reaction method. Single phases were formed easily for the first four compositions, and BaMgSi3O8 ceramics were found to be a mixture of both BaSi2O5 and MgSiO3, according to X‐ray diffraction results. Among all the compositions, Ba2MgSi2O7 ceramic sintered at 1225°C possesses the highest Qf (Q = 1/dielectric loss = 1/tanδ, f = resonant frequency) value ∼55 010 GHz along with relative permittivity ∼8.0 and temperature coefficient of resonant frequency (TCF) ∼−57.5 ppm/°C. With 3 wt.% BCB (BaO–B2O3–CuO) additions, Ba2MgSi2O7 ceramic was well densified at 950°C with a relative permittivity ∼8.1, Qf value ∼28 920 GHz (at 12.37 GHz) and TCF value ∼‒56.6 ppm/°C. These series ceramics with low relative permittivity values might be good candidates for low‐temperature co‐fire ceramic technology substrate applications. [ABSTRACT FROM AUTHOR]

Most polymer-based film capacitors experience severe degradation in electrical performance in high-temperature environments, making thermal stability a crucial factor for their stable use. This study prepared nanocomposites of polyimide mixed with three different particle sizes of nano-SiO2 particles using in situ polymerization methods. The experiment showed that filling the composites with different particle sizes of nano-SiO2 nanoparticles suppressed the leakage current density and significantly increased the breakdown field strength under high-temperature conditions. The nanocomposite containing 3 vol % 20 nm-SiO2/PI nanoparticles with high specific surface area exhibited excellent electrical performance, with a discharge energy density of 5.34 J cm–3 at 550 MV m–1 and 150 °C and an efficiency of 86.3%. The composite material also had an optical bandgap of 2.59 eV. Finite element simulations proved the accuracy and reasonableness of the experimental data. This study further verifies that high specific surface area nanofillers can indeed maximize the electrical performance of the composites, providing an example of the role of ultrafine nanoparticles in enhancing the harsh environment energy storage properties of polymers. [ABSTRACT FROM AUTHOR]

Microwave dielectric ceramics with intrinsic low sintering temperatures are potential candidates for low temperature co‐fired ceramics technology. In the present work, the (Li0.5Y0.5)MoO4 ceramic with tetragonal scheelite structures was selected to improve microwave dielectric properties of BiVO4 ceramics. As proved by X‐ray diffraction (XRD) results, scheelite structured solid‐solution ceramics were formed with x value ≤0.1 in the (Bi1−xLi0.5xY0.5x)(V1−xMox)O4. In situ XRD results further confirmed that the addition of (Li0.5Y0.5)MoO4 also lowered transition temperature from distorted monoclinic to tetragonal scheelite structure. When x value increased further, zircon phase was detected by XRD. Room and high‐temperature Raman spectra also supported the XRD results. Differences of thermal expansion coefficients of both monoclinic and tetragonal scheelite phases lead to an abnormality at phase transition temperature. Good microwave dielectric properties with permittivity above 70 and Qf (Q = quality factor = 1/dielectric loss and f = frequency) value above 8000 GHz were obtained in the (Bi1−xLi0.5xY0.5x)(V1−xMox)O4 solid‐solution ceramics with x value ≤0.1 sintered below 800°C. However, permittivity peak values at phase transition temperatures lead to large positive or negative temperature coefficient of resonant frequency, and this needs to be modified via composite technologies in the future. [ABSTRACT FROM AUTHOR]

Bismuth‐layered ferroelectric materials with Aurivillius structure are the potential materials for high‐temperature ferroelectric materials because of their high Curie temperature and excellent ferroelectric fatigue resistance. Herein, the Aurivillius phase relaxation ferroelectrics as Ban−3Bi4TinO3n+3 (n = 4–7) ceramics are studied. The layered structures are controlled by adjusting the number of BO6 octahedrons and (Bi2O2)2+ layers. The dielectric temperature stability and voltage resistance of bismuth barium titanate ceramics are improved. The influence of composition and microstructure on their electrical properties is explored. The relationship between dielectric properties and storage properties of bismuth barium titanate ceramics and the number of layers is obtained. Ba2Bi4Ti5O18 ceramics show the best performance with an energy storage density of up to 1.16 J cm−3 and a high efficiency of ≈87.2% (under 250 kV cm−1). This work provides key materials and technologies for the next generation of energy storage capacitors that can be applied in high‐temperature environments as well as a new reference for the development of dielectric materials and the functional optimization of other Aurivillius phase ceramic materials. [ABSTRACT FROM AUTHOR]

Lead‐free ceramics with high recoverable energy density (Wrec) and energy storage efficiency (η) are attractive for advanced pulsed power capacitors to enable greater miniaturization and integration. In this work, a series of perovskite structured (1‐x)(Bi0.6Ba0.4)(Fe0.6Ti0.4)O3−xNd(Zn2/3Nb1/3)O3 (BF‐BT‐NZN) ceramics with high energy storage density through the solid‐state reaction method are successfully prepared, and the breakdown strength (Eb) and energy storage density are further improved by a membrane rolling process. The highest energy densities of the 0.94(BF‐BT)−0.06NZN ceramics are Wrec ≈ 5.6 J cm−3 and η ≈ 82.9%, which are due to the enhanced breakdown field intensity (BDS ≈ 400 kV cm−1) and the maximum polarization (Pmax≈ 38 µC cm−2). These results indicate that (1−x)(Bi0.6Ba0.4) (Fe0.6Ti0.4)O3−xNd(Zn2/3Nb1/3)O3 ceramics are high‐efficiency lead‐free materials for potential application in high‐energy‐storage capacitors. [ABSTRACT FROM AUTHOR]