Crystal Structure, Chemical Bond, and Microwave Dielectric Properties of Ba_1-xSr_x(Zn_1/3Nb_2/3)O₃ Solid Solution...

Ba_1-xSr_x(Zn_1/3Nb_2/3)O₃ (BSZN) perovskite ceramics are prepared using the traditional solid-state reaction method. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS) were used to analyze the phase composition, crystal structure, and chemical states of BSZN ceramics, respectively. In addition, the dielectric polarizability, octahedral distortion, complex chemical bond theory, and PVL theory were investigated in detail. Systematic research showed that Sr²⁺ addition could considerably optimize the microwave dielectric properties of BSZN ceramics. The change in τ_f value in the negative direction was attributed to oxygen octahedral distortion and bond energy (E_b), and the optimal value of 1.26 ppm/°C was obtained at x = 0.2. The ionic polarizability and density played a decisive role in the dielectric constant, achieving a maximum of 45.25 for the sample with x = 0.2. The full width at half-maximum (FWHM) and lattice energy (U_b) jointly contributed to improving the Q × f value, and a higher Q × f value corresponded to a smaller FWHM value and a larger U_b value. Finally, excellent microwave dielectric properties (ε_r = 45.25, Q × f = 72,704 GHz, and τ_f = 1.26 ppm/°C) were obtained for Ba_0.8Sr_0.2(Zn_1/3Nb_2/3)O₃ ceramics sintered at 1500 °C for 4 h.