Effects of Synthesis Temperatures on Crystal Structures and Lattice Vibration Modes of (Ba_0.3Sr_0.7)[(Zn_1–x Mg _x )_1/3Nb_2/3]O₃ Solid Solutions

(Ba_0.3Sr_0.7)[(Zn_1–x Mg _x )_1/3Nb_2/3]O₃ (BSZMN, x = 0.4, 0.6, and 0.8) solid-solution ceramics were synthesized by the conventional solid-state synthesis technique. X-ray diffraction (XRD) and vibration spectra (Raman spectroscopy and Fourier transform far-infrared reflection spectroscopy) were employed to evaluate effects of synthesis temperatures on crystal structures and lattice vibration modes of these solid solutions. The XRD results reveal that BSZMN ceramics have a phase transformation, from pseudocubic structure to hexagonal distorted perovskite structure with different Mg²⁺ concentration and different synthesis temperatures, i.e., symmetry decreases with increasing synthesis temperatures. From Raman spectra, synthesis temperatures have an obvious influence on the phonon modes, which are closely related to the 1:2 ordered structure. Variation of the phonon parameters corresponds to the ordering degree; however, the phase transformation and the second phase can influence the phonon characteristics. The results are also proved by far-infrared reflection analyses.