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We investigate the hydrostatic pressure dependences of elastic, electronic, and optical properties of the newly hypothesized perovskite compound ACuO3 (A = Ca, Sr) using the first-principles method. The structural and mechanical stabilities have been established theoretically under pressure up to 100 GPa. The ductile nature of these transition metal oxides has been confirmed by the calculation of elastic constants. The relatively low-value Young's modulus possesses high thermal shock resistance and proclaims the materials to be a promising thermal barrier coating material. The partial density of states shows the dominant behavior of Cu-3 d and O-2 p orbitals at the Fermi level and it implies the subsequent good electrical conductivity. The significant response of the optical properties such as reflectivity, dielectric constant, optical absorption, and loss function with the change in pressure have been noted. The origin of these optical responses is discussed with implications, which can be supportive for future investigations of ACuO3 (A = Ca, Sr). [ABSTRACT FROM AUTHOR]

Perovskite oxides with the general formula ABO3 comprise a large number of families among the structures of oxide-based materials, and currently, several perovskite structures have been identified. From a variety of compositions and structures, various functions are observed in perovskite compounds, and therefore, they became very useful for various applications in the electronic and medical industries. One of the most puzzling issues for perovskite compounds is the understanding of the vibration and relaxation dynamics in the gigahertz range. In that sense, the micro-Brillouin scattering system is a very effective tool to probe the gigahertz dynamics, and also, first-principles calculations can be used to describe the phonon structure with different atomic contributions. The micro-Brillouin scattering system and first-principles calculations provide the fundamental information on a variety of vibration and relaxation processes related to structural phase transitions under different external conditions such as temperature, electric field, and pressure. This review article summarizes the Brillouin scattering and first-principles studies on BaMO3 (M = Ti, Zr, and Cu). Through a detailed analysis of the existing results, we summarize the existing limitations and future perspectives in these research areas, which may propel the development of different perovskite ferroelectrics and extend their practical application areas. [ABSTRACT FROM AUTHOR]

The analysis of local polar clusters formed by random fields in ferroelectrics is of technical and fundamental importance in understanding piezoelectricity. The temperature and electric field dependences of elastic properties and the ferroelectric phase transition have been investigated in (100)-oriented BaTiO3 single crystals by micro-Brillouin scattering. In the field cooling process, LA phonons are scattered by polar clusters. As a result, the LA phonon frequency increases as compared with that of the zero-field cooling process. Under the application of an external electric field along the [100] direction in the tetragonal ferroelectric phase, a complete 90° domain switching is accomplished. Under the electric field, abrupt changes in the frequency shift and FWHM of the LA phonons in the paraelectric cubic phase indicate the occurrence of a phase transition from the cubic to the tetragonal phase. An E – T phase diagram has been proposed from the field-induced phase transition. [ABSTRACT FROM AUTHOR]

Brillouin scattering was measured on a ferroelectric 0.44Pb(Mg1/3Nb2/3)O3-0.56PbTiO3(PMN-56PT) single crystal with weak quenched random fields in the polarized (VV) and depolarized (VH) scattering geometries over a wide temperature range. The VH- and VV- central peaks (CPs) related to the transverse and longitudinal polarization fluctuations of polar nanoregions (PNRs) were successfully observed in a paraelectric cubic phase. The inverse relaxation time (1/τCP) determined by the VH-CP indicates the stretched slowing down above the Curie temperature (∼ 533 K). The temperature dependence of the average size of dynamic PNRs was estimated. [ABSTRACT FROM PUBLISHER]

Elastic properties of relaxor ferroelectric 0.44Pb(Mg1/3Nb2/3)O3-0.56PbTiO3single crystals have been studied under zero and external electric field along [100]-direction by micro-Brillouin scattering. Here we show the ability to move the ferroelectric multidomains toward a single domain state by the application of electric field. In the vicinity of TC-T= 260°C, the anomalous change of C11in a paraelectric cubic phase was well reproduced by the power law which exhibits the three dimensional polarization fluctuations. The order-disorder nature of the ferroelectric phase transition was confirmed by the analysis of sound attenuation based on the theoretical model by Levanyuk et al. [ABSTRACT FROM AUTHOR]