Microwave dielectric ceramics should be improved to advance mobile communication technologies further. In this study, we prepared Sr1+xY2O4+x(x = 0–0.04) ceramics with nonstoichiometric Sr2+ ratios based on our previously reported SrY2O4 microwave dielectric ceramic, which has a low dielectric constant and an ultrahigh quality factor (Q value). The ceramic exhibited a 33.6% higher Q-by-frequency (Q×f) value (Q ~12,500) at x = 0.02 than SrY2O4. All Sr1+xY2O4+x(x = 0–0.04) ceramics exhibited pure phase structures, although variations in crystal-plane spacings were observed. The ceramics are mainly composed of Sr-O, Y1-O, and Y2-O octahedra, with the temperature coefficient of the resonant frequency (τf) of the ceramic increasing with Y2-O octahedral distortion. The ceramic comprises uniform grains with a homogeneous elemental distribution, clear grain boundaries, and no obvious cavities at x = 0.02. The Sr1+xY2O4+x(x = 0–0.04) ceramics exhibited good microwave dielectric properties, with optimal performance observed at x = 0.02 (dielectric constant (εr) = 15.41, Q×f = 112,375 GHz, and τƒ = −17.44 ppm/℃). The τf value was reduced to meet the temperature-stability requirements of 5G/6G communication systems by adding CaTiO3, with Sr1.02Y2O4.02+2wt%CaTiO3 exhibiting εr = 16.14, Q×f = 51,004 GHz, and τf= 0 ppm/℃. A dielectric resonator antenna prepared using Sr1.02Y2O4.02+2wt%CaTiO3 exhibited a central frequency of 26.6 GHz, with a corresponding gain and efficiency of 3.66 dBi and 83.14%, respectively. Consequently, Sr1.02Y2O4.02-based dielectric resonator antennas are suitable for use in 5G millimeter-wave band (24.5–27.5 GHz) applications.
Addition of xanthine 0.42 mmol.L-1 and xanthine oxidase 5.3 nmol.L-1 (X-XO) to the culture medium increased the amplitude of ESR spectra of myocardial cells, demonstrating an increase in free radical contents; diminished the action potential parameters significantly and reduced the input impedances from 0.34 +/- 0.11 to 0.24 +/- 0.1 M omega, expressing a typical electrical appearance of membrane damage. Supplying Cu 62.5 ng.ml-1 and/or Se 173 ng.ml-1 to the medium brought all of the electric parameters and the free radical content of myocardial cells back to normal. The results indicate that both the two trace elements are able to scavenge free radicals, thus antagonizing X-XO, which induces damage to myocardial cells.
The structural characteristics of Ca 3 Mn 2+ x Ge 3 O 12+ δ ( x = 0.1) ceramics correspond to their excellent microwave dielectric properties: ε r = 8.88, Q × f = 50 793 GHz, τ f = −39.35 ppm °C −1 .
Polyethylene glycol was used in a sol-gel route to prepare gadolinium titanate.The crystallite sizes of pyrochlore Gd 2 Ti 2 O 7 prepared at 800°C and 900°C were 34.2 and 40.0 nm, respectively.Pores were produced in the materials after removing the PEG1000 template.The bandgap energies of Gd 2 Ti 2 O 7 decreased from 3.43 to 3.21 eV when the calcination temperature increased from 600°C to 900°C.The crystallized porous Gd 2 Ti 2 O 7 had a low photoluminescence intensity.The samples prepared at low calcination temperatures had both a large pore volume and a high specific surface area, and the Brunauer-Emmett-Teller surface area decreased from 46.8 to 14.9 m 2 /g when the calcination temperature increased from 600°C to 900°C.Hydroxyl radical production and azo dye degradation proved the strongest photocatalytic activity of porous Gd 2 Ti 2 O 7 calcined at 800°C.The Reactive Brilliant Red X-3B degradation efficiency was 43.5% after 30 min of reaction.
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