Guo Tian,Linzhao Ma,Qianbiao Du,Longxiang Jiang,Hongzhi Xiao,Hao Li
A novel type of Li 3 NbO 4 –Li 2 TiO 3 - x MgO (LLM x , x = 1–5) ceramics were prepared using the solid-state reaction method. When the sintering temperature is between 1180 °C and 1300 °C, the solid solution ceramics with cubic rock salt structure are obtained. As the MgO content increases, the ε r value decreases, the τ f value is basically constant, and Q×f exhibits ideal dielectric properties at x = 4 ( ε r = 15.26, Q×f = 119,456 GHz ( f = 9.97 GHz), τ f = −35.9 ppm/°C). The Raman spectrum analysis was used to examine and understand the vibration mode and intrinsic mechanism of dielectric properties in ceramics. Additionally, a dielectric resonant antenna based on LLM 4 ceramic is fabricated with a resonant frequency of 7.23 GHz (|S 11 | = −45.6 dB), a higher gain and broadband width of 501 MHz.
Xiaojian Fan,Qianwan Qin,Dongming Liu,Aichun Dou,Mingru Su,Yunjian Liu,Jun Pan
In this reported study, Li 3 NbO 4 -based, Li-excess cathode materials xLi 3 NbO 4 •(1-x)LiMnO 2 (0.2 ≤ x ≤ 0.5) were synthesized using a solid state reaction method. XRD results showed that the fabricated powders with x = 0.3–0.5 could be indexed to a typical rock-salt structure (Fm-3m space group). Rietveld refinements showed that the lattice parameters increased with the increase in Nb 5+ content. SEM and TEM images of the product showed that the elements Nb, Mn and O were evenly distributed in the samples, which further confirmed the cubic rock-salt structure of the product. Electrochemical tests of the samples showed that the sample with x = 0.4 exhibited the best electrochemical performance (232 mAh/g in the first cycle and more than 175 mAh/g in 50 cycles, as well as relatively high discharge capacity at high discharge current density). The redox mechanism analysis of the experimental results indicated that there were two stages in charge process: one was the Mn 3+/4+ oxidation reaction below 4.3 V, and the other was related to the oxidation of O 2− to O − or the release of O 2 , which improved the reversible capacity of the material. The structural evolution analysis of the samples showed that a spinel phase structure was present during the cycling process and the shift in the XRD peaks indicated that the sample with x = 0.4 exhibited the best structural stability. The electrochemical impedance spectroscopy analysis showed that the sample with x = 0.4 had the smallest R ct . The results for the kinetics of lithium ion diffusion indicated that the sample with x = 0.4 had largest D Li +, which was consistent with the best electrochemical performance for this material, especially the rate capability.
危险品化学品经营许可证（带存储）