The effect of Sm2O3 on the sintering and grain growth behaviors of SnO2-based ceramics

The effect of samarium oxide was examined on the sintering, microstructure, and grain growth behaviors of (Co, Nb)-doped SnO2-based ceramics prepared by co-precipitation method. The sintered samples were studied through x-ray diffraction (XRD), scanning electron microscopy (SEM), and electron dispersive spectroscopy (EDS) analyses. The microstructure observations revealed that the samples were near fully dense at a sintering temperature of 1200°C for 1h. The samarium doping prevented accelerated grain growth of the SnO2-based ceramic in the final stage of the sintering. The mean grain size of the SnO2-based ceramic without Sm2O3 doping was 2.70μm, which was reduced to 0.887μm for the sample doped with 0.05mol% Sm2O3. The grain size reduction of samples doped with Sm2O3 could be attributed to the segregation of Sm2O3 at the grain boundaries

High-Qf value and temperature stable Zn2+-Mn4+ cooperated modified cordierite-based microwave and millimeter-wave dielectric ceramics

Cordierite-based dielectric ceramics with a lower dielectric constant would have significant application potential as dielectric resonator and filter materials for future ultra-low-latency 5G/6G millimeter-wave and terahertz communication. In this article, the phase structure, microstructure and microwave dielectric properties of Mg2Al4–2x(Mn0.5Zn0.5)2xSi5O18 (0 ≤ x ≤ 0.3) ceramics are studied by crystal structure refinement, scanning electron microscope (SEM), the theory of complex chemical bonds and infrared reflectance spectrum. Meanwhile, complex double-ions coordinated substitution and two-phase complex methods were used to improve its Q×f value and adjust its temperature coefficient. The Q×f values of Mg2Al4–2x(Mn0.5Zn0.5)2xSi5O18 single-phase ceramics are increased from 45,000 [email protected] GHz (x = 0) to 150,500 [email protected] GHz (x = 0.15) by replacing Al3+ with Zn2+-Mn4+. The positive frequency temperature coefficient additive TiO2 is used to prepare the temperature stable Mg2Al3.7(Mn0.5Zn0.5)0.3Si5O18-ywt%TiO2 composite ceramic. The composite ceramic of Mg2Al3.7(Mn0.5Zn0.5)0.3Si5O18-ywt%TiO2 (8.7 wt% ≤ y ≤ 10.6 wt%) presents the near-zero frequency temperature coefficient at 1225 °C sintering temperature: εr = 5.68, Q×f = 58,040 GHz, τf = −3.1 ppm/°C (y = 8.7 wt%) and εr = 5.82, Q×f = 47,020 GHz, τf = +2.4 ppm/°C (y = 10.6 wt%). These findings demonstrate promising application prospects for 5 G and future microwave and millimeter-wave wireless communication technologies

(Co, Nb, Sm)-Doped tin dioxide varistor ceramics sintered using nanopowders prepared by coprecipitation method

(Co, Nb, Sm)-doped SnO2-based ceramic with varistor characteristics was successfully fabricated by a conventional sintering of nanosized (Co, Nb, Sm)-doped SnO2 powders prepared by coprecipitation method. Values of α∼38 and EB=1430 V/mm were obtained for the varistor doped with 0.05 mol % Sm2O3, sintered at 1200°C for 1 h. Microstructure development was studied by scanning and transmission electron microscopy, elemental analysis, and X-ray diffraction. The mean grain size of the SnO2-based varistor was 1.75 μm. No other phase besides SnO2 was observed in the varistor doped with 0.05 mol % Sm2O3. The presence of Nb, Co, and Sm inside the SnO2 grains confirmed the formation of solid solution. No segregation of Nb was observed and Nb atoms were homogeneously distributed. The excess amounts of Co were segregated at triple-junctions between SnO2 grains. A Sm-rich region with a typical thickness of 65 nm was observed at the grain boundary of the varistor

Crystal Structure and Microwave Dielectric Property of <i>x</i>MgO-SiO₂ (<i>x</i> = 1~2) System for 5G Applications

Mg2SiO4 and MgSiO3 ceramics with superior microwave dielectric properties are considered to be promising candidates for 5G applications. However, a slight deviation from the stoichiometric Mg/Si ratio will significantly influence their microwave dielectric properties, which will hinder their practical applications. In this work, the xMgO-SiO2 (x = 1~2) ceramics were synthesized by a solid-state reaction method. The influence of the Mg/Si ratio x on the crystalline phase, microstructure, and microwave dielectric properties was investigated through X-ray diffraction (XRD), a scanning electron microscope (SEM), and the resonant cavity method. The XRD patterns revealed the coexistence of Mg2SiO4 and MgSiO3 within the x range of 1~2, which was further demonstrated by the energy-dispersive X-ray spectra. The SEM images show a typical polycrystalline morphology of ceramics with an inhomogeneous grain size distribution. It is found that the microwave dielectric properties fluctuate at both sides of the x range while those remain relatively stable with minor changes at the intermediate components, indicating an obvious low composition dependence helpful for practical applications. Further, a demonstrator of a microstrip patch antenna for 5G applications using the 1.5MgO-SiO2 ceramic was designed and fabricated, and a return loss of −16.2 dB was demonstrated, which demonstrated the potential applications