Disorder‐induced symmetry lowering in Ba(Y_1/2Nb_1/2)O₃ ceramics probed by Raman spectroscopy

Abstract

This work investigates the evolution of the crystal structure of microwave-hydrothermal synthesized Ba(Y 1/2 Nb 1/2 )O 3 powders as a function of firing temperature by Raman spectroscopy. The samples were produced at 200°C and fired at temperatures ranging from 600 to 1600°C. Raman spectra were obtained at room temperature for all samples and the results showed that materials fired at 1600°C exhibited tetragonal (I4/m or C 5 4h ) structure, whereas those fired at lower temperatures exhibited the triclinic (P1 or C 1 i ) structure. The results were compared with those observed for ceramics obtained by conventional solid-state methods. It is believed that the lowering of the symmetry verified in materials fired below 1600°C is a consequence of the local disorder of Y +3 and Nb +5 ions in octahedral sites.

Raman signatures of monoclinic distortion in (Ba1−xSrx)3CaNb2O9 complex perovskites

“…Furthermore, Raman spectroscopy is applied to detect the local structure disturbance induced by symmetry lowering. As reported by many authors, the combination of Raman scattering and factor‐group analysis is an important tool to investigate the structural changes in perovskites and related compounds through the optical phonon behavior at the first‐Brillouin zone ( q ≈ 0). This approach will be used here to assign our Raman results.…”

Crystal structure of fluorite-related Ln3SbO7 (Ln=La–Dy) ceramics studied by synchrotron X-ray diffraction and Raman scattering

“…In this context, the present paper intends to contribute to the elucidation of the possible crystal structure of Ln 3 SbO 7 ceramics (Ln ¼La-Dy, exception of Ce and Pm), by reporting on our results of Raman scattering, second harmonic generation and synchrotron X-ray powder diffraction (SXRD). A similar methodology was previously applied by our group to solve structural conflicts for many materials [30][31][32][33].…”

Optical-active phonons in A3Fe2B″O9 (A=Ca, Sr; B″=Te, W) double perovskites

“…Raman and infrared spectroscopy provide valuable insight into order-disorder phenomena and are very sensitive to sample composition and structural variations, making it suitable for studying the effects of atomic substitutions in complex perovskites. [17][18][19][20][21] There has been an increasing interest in the study of A 3 Fe 2 BЉO 9 ͑A = Ca, Sr; BЉ = Te, W͒ double perovskites, which exhibit exciting ferromagnetic properties at room temperature. [2][3][4][5][6][7] The Sr 3 Fe 2 WO 9 ͑SFWO͒ and Ca 3 Fe 2 WO 9 ͑CFWO͒ compounds have been investigated by neutron powder diffraction by Ivanov et al, 2,3 who determined that SFWO crystallizes at 300 K in a tetragonal structure belonging to the space group I4 / m, while CFWO crystallizes in a monoclinic structure belonging to the space group P2 1 / n. Identical results have been obtained for CFWO by Retuerto et al 22 These compounds exhibit a partially ordered double perovskite structures, in which the Fe and W cations are orderly distributed at the BЈ-and BЉ-symmetry sites of the perovskite lattice.…”