Temperature-dependent Raman spectroscopy measurements in Y2NiMnO6 ceramics were performed in the 20 K–850 K range. A detailed analysis of the temperature dependence of the phonon energy of the oxygen octahedra stretching mode shows an anomalous softening below the Curie temperature. This effect was ascribed to a spin-phonon coupling, suggesting that the oxygen octahedra stretching vibrational mode stabilizes the magnetic interaction. The observed spin-phonon coupling is stronger than those reported in other Re2NiMnO6 double perovskites, suggesting that the rare earth ionic radius is not the unique parameter influencing the magnitude of this effect.

Low-dimensional metal halide compounds, usually described as low-dimensional perovskites, present exciting properties as functional materials for a broad range of optoelectronic applications. These compounds are characterized by intense photoluminescence (PL), a narrow emission line width, and a high exciton binding energy. In particular, the mechanism behind the strong green emission of the zero-dimensional compound Cs 4 PbBr 6 has been the subject of intense debate. As a propertytuning tool, hydrostatic pressure was used to investigate the structural and optical properties of bulk Cs 4 PbBr 6 through synchrotron X-ray diffraction combined with Raman and PL spectroscopies. As a result, two structural phase transitions at 3.2 and 4.6 GPa were identified, with the latter not observed in previous investigations performed on nanocrystals. Also, the pressure dependence of the PL emission was recorded and compared with the previous results on Cs 4 PbBr 6 and CsPbBr 3 nanocrystals. Under the ambient conditions, strong green emission exhibits a subtle redshift, followed by a blueshift under pressure, being associated first with an intensity enhancement and subsequent quenching above 3 GPa. These results support the CsPbBr 3 luminescent inclusions as the PL emission mechanism in Cs 4 PbBr 6 .

In this work, we have performed Raman scattering measurements in Ba 2 BiSbO 6 ceramics in the temperature range from 10 to 573 K. The Raman spectra were examined using group theory to analyze the decomposition of the reducible representation of the vibrational modes and with a virtual octahedral model. At room temperature, five modes were observed. At low temperatures, the spectra subtly showed the rhombohedral-monoclinic phase transition, which was identified by changes in the Raman intensity of the bending and symmetrical stretching SbO 6 octahedral modes. The cubic-rhombohedral phase transition was not clearly evident in the high-temperature Raman data.

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The electric properties of the complex double perovskite Ba 2 BiSbO 6 have been investigated using impedance spectroscopy in the frequency range from 1 Hz up to 1 MHz and in the temperature range from room temperature up to 560 K. There are two contributions to the electrical properties due to the grain and grain boundary. The oxygen vacancies play an important role in the conductivity and strongly increase the dielectric constant at high temperatures. The analysis of the frequency dependence of the conductivity clearly shows the structural phase transition of this compound near 515 K.