(ZnMg)₂SiO₄ powders was prepared by the sol–gel process, and the microstructure and dielectric properties of (Zn_1–𝑥Mg_𝑥)₂SiO₄ microwave materials were investigated systematically. TG-DSC and XRD analyzes for gels indicate that the (ZnMg)₂SiO₄ with pure willemite phase could be obtained at low temperature of 850°C. Further, XRD illustrates that just small amounts of Mg can be incorporated into Zn₂SiO₄ lattice, and the solid solution limit of Mg in Zn₂SiO₄ is about 𝑥 = 0.1. By appropriate Mg substitution for Zn, the sintering range is widened and the sintering temperature of Zn₂SiO₄ ceramics can be lowered effectively. SEM shows that Mg-substitution for Zn can promote the grain growth of Zn₂SiO₄. Moreover, the microwave dielectric properties strongly depended on the substitution content of Mg and sintering temperatures. (Zn_0.8Mg_0.2)₂SiO₄ dielectrics sintered at 1170°C show the condense microstructure with small uniform grains and best microwave properties: 𝜀_r = 6.3, 𝑄 × 𝑓 = 189800 GHz and 𝜏_f = –63 ppm/°C.

The NASICON-type Na$_3$V$_2$(PO$_4$)$_3$ (NVP) material was synthesized through the sol–gel route and characterized as cathode in sodium-ion battery by the cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) as well as electrochemical impedance spectroscopy (EIS) methods. Scan rate-dependent CV demonstrates an approximate diffusion-type behaviour and gives the diffusion coefficient value 5.24 ${\times}$ 10$^{–11}$ cm$^2$ s$^{–1}$ for Na$^+$ in NVP. Both GITT and EIS tests demonstrate the U-shape diffusion coefficients for Na$^+$ correlated to stoichiometry ranging from 10$^{–16}$ to 10$^{–11}$ cm$^2$ s$^{–1}$, where bottom of the diffusion rate corresponding the plateau voltage well matches with CV data. The strong interaction between the main skeleton and Na$^+$ during the two-phase reaction as demonstrated by the X-ray diffraction results was believed as the reason that reduces the diffusion rate of Na$^+$ at the plateau voltage.