The development of polar order in perovskite-type (ABO 3 ) solid solutions of relaxors and normal ferroelectrics is studied on the basis of the temperature dependence of polarized Raman spectra of pure and Ru-doped 0.9PbZn 1/3 Nb 2/3 O 3 -0.1PbTiO 3 (PZN-0.1PT) single crystals as well as complementary x-ray diffraction analysis. It is shown that the Raman peaks related to Pb-localized vibrations existing solely in a double-perovskite structure (prototype symmetry F m3m) are highly sensitive to the nucleation and development of polar atomic arrangements. The doublet near 50 cm −1 observed in the high-temperatureZ(XY )Z spectra of PZN-xPT (x = . The singlet in the high-temperatureZ(XY )Z spectra is assigned to off-centered Pb2 ions. The Raman spectra of PZN-0.1PT indicate that off-centered Pb2 ions induce coherent polar shifts of ferroelectrically active B cations, which in turn facilitates the off-centering of Pb1 ions. A low degree of B-site doping with mixed-valence elements like Ru can substantially influence the development of ferroelectric order in PZN-xPT solid solutions due to the different preferred types of local octahedral distortion associated with the different valence states of the doping cations. The incorporation of Ru into the structure of PZN-0.1PT slightly decreases the Burns temperature and shifts the tetragonal-to-monoclinic phase transition to lower temperatures, thus favoring the tetragonal state in a wider temperature range as compared to the undoped compound. An assumption is made that the nanoscale polar order in Pb-based B-site complex perovskite-type relaxors might be of ferrielectric type rather than of ferroelectric type.

The pressure-induced structural changes in perovskite-type (ABO 3 ) Pb-based relaxor ferroelectrics are studied on the basis of in situ single-crystal synchrotron x-ray diffraction and Raman scattering experiments on PbSc 0.5 Ta

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We present the results of a comprehensive study linking the crystal‐chemical formulae of amphiboles, a series of extremely complex silicates with the general formula (AB2C5T8O22W2, C5 = M12M22M3) to variations in the peak positions, widths, and intensities of the Raman‐active modes. To this purpose, we have analyzed the Raman scattering generated by the framework vibrations (15–1,215 cm−1) and by the OH‐stretching modes (3,000–4,000 cm−1) of 44 samples, spanning all six major subgroups. We show that, in addition to the information that can be derived from the OH‐stretching range (Leissner et al., Am. Mineral. 2015, 100, 2682), further important features of the amphibole structure, composition, and cationic site population can be directly extracted from the framework Raman spectrum, namely, (a) the distinction between the monoclinic and orthorhombic symmetries; (b) the estimation of TAl content, when TAl > 0.5 apfu; (c) the estimation of CTi content, when CTi > 0.3 apfu; (d) the estimation of CLi content, when CLi > 0.3 apfu; (e) the detection of CAl, when CAl > 0.7 apfu; (f) an estimate of CMg; (g) the estimation of CFe3+ in the case of Na amphiboles; and (h) the estimation of the Fe2+ content at the M2 site in the case of Mg–Fe–Mn amphiboles. Additionally, we point out that the TO4‐ring‐breathing mode near 670 cm−1, which is commonly used to fingerprint various amphibole species, has to be handled with a great care, because it is sensitive to the site population at all crystallographic sites.