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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]

Lead-free ceramics are important in the sustainable advancement of energy storage techniques owing to their exceptional density of power, commendable resistance to high temperatures, and non-toxic nature. However, lead-free ceramics are no longer aligned with the requirements for the miniaturization and light weighting of electronic components because of their limited energy density and conversion efficiency. In this study, the storage performance of lead-free ceramics was optimized by constructing (1 − x)(Ba0.8Sr0.2)TiO3–xBi(Zn2/3Ta1/3)O3 ceramics using a cooperative optimization strategy. This strategy involved utilizing Bi(Zn2/3Ta1/3)O3 to induce polar nano-regions, contributing to an increase in Eb and a reduction in Pr, thereby enhancing the energy storage properties. Notably, the 0.91(Ba0.8Sr0.2)TiO3–0.09Bi(Zn2/3Ta1/3)O3 relaxation ferroelectric ceramic demonstrated the ability to simultaneously achieve an ultra-high Wrec of 5.53 J cm−3 and an excellent η of 93.6% at a relatively high electric field intensity of 460 kV cm−1. Furthermore, the samples exhibited a high η (∼96%) in the 5–100 Hz frequency range and in the 30–100 °C temperature range. The collective outstanding performance of the 0.91(Ba0.8Sr0.2)TiO3–0.09Bi(Zn2/3Ta1/3)O3 ceramic substantiates its immense potential for utilization in pulse power capacitors. [ABSTRACT FROM AUTHOR]

Low dielectric constant (ɛr), high quality‐factor (Q × f), and temperature stable microwave dielectric ceramics with ultra‐low sintering temperature are the preferred choice of researchers for the development of low‐cost and high‐performance dielectric resonator antenna (DRA), which have wide application prospects for wireless communication technology. In this work, wideband DRAs fabricated using ultra‐low sintering temperature, low‐loss, and high‐quality Li6B4O9 microwave dielectric ceramics are reported. Li6B4O9 ceramic synthesized via solid‐state reaction at sintering temperature of 620 °C demonstrates excellent microwave properties with optimum ɛr = 5.95, high Q × f = 38,700@12.4 GHz, and thermal coefficient of the resonant frequency (TCF ≈ −68.6ppm/○C). For the first time, performance comparison of two Li6B4O9‐based cylindrical DRAs with different ceramic aspect (radius to height) ratios excited by slot coupled microstrip line is realized. In the first DRA with ceramic aspect ratio of 0.864, DRA HE11δ mode is excited and bandwidth of 20.01% , 95% radiation efficiency, and 6.3 dBi maximum gain is attained. In the second DRA with ceramic aspect ratio of 2.367, slot and dielectric resonator resonances are merged to attain wide bandwidth of 38.15% over which antenna broadside radiation performance is preserved. The proposed DRAs can be utilized for high‐capacity, high‐speed wireless communication applications. [ABSTRACT FROM AUTHOR]

(CoxZn1–x)TiNb2O8 (x = 0.2–0.8) microwave dielectric ceramics were synthesized via the conventional solid‐state reaction route, and the correlation of microwave dielectric properties on the crystal structure was discussed. Crystal structures of ceramic samples were systematically investigated by X‐ray powder diffraction. Moreover, composition‐induced phase transitions were confirmed via the following sequence: for x ≤ 0.2, single‐phase orthorhombic ixiolite (ZnTiNb2O8) was formed, whereas for 0.3 ≤ x<0.8, ixiolite and rutile coexisted. When x ≥ 0.8, only single‐phase rutile was detected. For the (CoxZn1–x)TiNb2O8 ceramics, the microwave dielectric properties were changed with the crystal structural transitions: the dielectric constant (εr) and the temperature coefficient of resonant frequency (τf) increased upon increasing the Co2+, but the quality factor (Q) decreased. A near‐zero τf = +1.6 ppm/°C was obtained in the Co0.38Zn0.62TiNb2O8 ceramics with εr = 40.7 and high Q × f = 16 790 GHz. These research outcomes are expected to have great significance for developing microwave dielectric ceramics in practical applications. [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]

In developing low-temperature cofired ceramic (LTCC) technology for high-density packaging or advanced packaged electronics, matching the coefficient of thermal expansion (CTE) among the packaged components is a critical challenge to improve reliability. The CTEs of solders and organic laminates are usually larger than 16.0 ppm of °C 1- , while most low-permittivity (ε r ) dielectric ceramics have CTEs of less than 10.0 ppm °C 1- . Therefore, a good CTE match between organic laminates and dielectric ceramics is required for further LTCC applications. In this paper, we propose a high-CTE BaSO 4 -BaF 2 LTCC as a potential solution for high-reliability packaged electronics. The BaSO 4 -BaF 2 ceramics have the advantages of a wide low-temperature sintering range (650-850 °C), low loss, temperature stability, and Ag compatibility, ensuring excellent performance in LTCC technology. The 95 wt %BaSO 4 -5 wt %BaF 2 ceramic has a ε r of 9.1, a Q × f of 40,100 GHz @11.03 GHz ( Q = 1/tan δ), a temperature coefficient of the resonant frequency of -11.2 ppm °C 1- , a CTE of +21.8 ppm °C 1- , and a thermal conductivity of 1.3 W mK -1 when sintered at 750 °C. Furthermore, a dielectric resonant antenna using BaSO 4 -BaF 2 ceramics, a typically packaged component of LTCC and laminate, was designed and used to verify the excellent performance by a gain of 6.0 dBi at a central frequency of 8.97 GHz and a high radiation efficiency of 90% over a bandwidth of 760 MHz. Good match and low thermal stress were found in the packaged components of BaSO 4 -BaF 2 ceramics, organic laminates, and Sn-based solders by finite element analysis, proving the potential of this LTCC for high-reliability packaged electronics.

Vanadium(V)-substituted cerium niobate [Ce(Nb 1- x V x )O 4 , CNV x ] ceramics were prepared to explore their structure-microwave (MW) property relations and application in C-band dielectric resonator antennas (DRAs). X-ray diffraction and Raman spectroscopy revealed that CNV x (0.0 ≤ x ≤ 0.4) ceramics exhibited a ferroelastic phase transition at a critical content of V ( x c = 0.3) from a monoclinic fergusonite structure to a tetragonal scheelite structure (T F-S ), which decreased in temperature as a function of x according to thermal expansion analysis. Optimum microwave dielectric performance was obtained for CNV0.3 with permittivity (ε r ) of ∼16.81, microwave quality factor ( Qf ) of ∼41 300 GHz (at ∼8.7 GHz), and temperature coefficient of the resonant frequency (TCF) of ∼ -3.5 ppm/°C. ε r is dominated by Ce-O phonon absorption in the microwave band; Qf is mainly determined by the porosity, grain size, and proximity of T F-S ; and TCF is controlled by the structural distortions associated with T F-S . Terahertz (THz) (0.20-2.00 THz, ε r ∼ 12.52 ± 0.70, and tan δ ∼ 0.39 ± 0.17) and infrared measurements are consistent, demonstrating that CNV x (0.0 ≤ x ≤ 0.4) ceramics are effective in the sub-millimeter as well as MW regime. A cylindrical DRA prototype antenna fabricated from CNV0.3 resonated at 7.02 GHz (| S 11 | = -28.8 dB), matching simulations, with >90% radiation efficiency and 3.34-5.93 dB gain.