Search results for "Electricity"
showing 10 items of 1225 documents
Kinetics of dielectric response in SBN-75 ceramics at infra-low frequencies under illumination
2014
A study of the photo-dielectric effect in ferroelectric SBN-75 ceramics of a broad phase transition under light of small intensity is reported. Relations determining kinetics of the infra-low frequency dielectric response under light and after illumination are obtained from experimental measurements revealing the features of the behaviour of relaxation time constants of the dielectric polarisation with temperature.
Novel octahedral tilt system a + b + c + in (1 − x)Na0.5Bi0.5TiO3–xCdTiO3 solid solutions
2017
This work has been supported by National Research Program in the framework of project “Multifunctional Materials and composites, photonics and nanotechnology (IMIS2)”.
Quasiclassical free energy of superconductors : Disorder-driven first-order phase transition in superconductor/ferromagnetic-insulator bilayers
2020
In the seminal work by G. Eilenberger, Z. Phys. 214, 195 (1968), a closed-form expression for the free energy of inhomogeneous spin-singlet superconductor in terms of quasiclassical propagators has been suggested. However, deriving this expression and generalizing it for superconductors or superfluids with general matrix structure, e.g., spin-triplet correlations, has remained problematic. Starting from the Luttinger-Ward formulation, we discuss here the general solution. Besides ordinary superconductors with various scattering mechanisms, the obtained free-energy functional can be used for systems, such as superfluid $^{3}\mathrm{He}$ and superconducting systems with spatially inhomogeneou…
Dielectric and Polarization Properties of Na0.5Bi0.5TiO3-BaTiO3Solid Solutions with Na and K Niobates
2015
The role of substitution in A- and B-sites of perovskite ABO3 structure in phase transitions is evaluated, comparing (1-y)(0.939Na0.5Bi0.5TiO3-0.061BaTiO3)-yKxNa1-xNbO3 solid solutions with x = 0.0, x = 0.5 and x = 1.0. The influence of deviation from a stoichiometric Na/Bi ratio is also studied. The influence of K0.5Na0.5NbO3, NaNbO3 or KNbO3 reduces mainly to suppressing of ferroelectric properties, like in other perovskite ferroelectrics where Ti is replaced by Nb, and development of the relaxor state. Besides the frequency-dependent dielectric permittivity, the relaxor state in the studied compositions is characterized also by a temperature dependence of critical electric fields, corres…
Interpretation of the Electrocaloric Effect in Na1/2Bi1/2TiO3-SrTiO3-PbTiO3Solid Solutions
2015
Results of direct measurements of electrocaloric effect and polarization are mutually compared in solid solutions 0.4Na1/2Bi1/2TiO3-(0.6-x)SrTiO3-xPbTiO3. Three temperature regions are distinguished in respect of a phase transition temperature. Above the phase transition, electrocaloric effect is determined by orientation of polar nanoregions by electric field. In wide temperature regions above and below the phase transition temperature, the difference between results, obtained from direct electrocaloric effect measurements and from polarization hysteresis loops, is explained by temperature dependence of concentration of polar nanoregions, oriented by electric field. Existence of a common Δ…
Comparative studies of ferroelectric and magnetic phase transitions in Pb(Fe1/2Nb1/2)O3-PbMO3 (M-Ti, Zr) multiferroic solid solutions
2015
Some peculiar features of magnetic x,T-phase diagram of (1-x)PbFe1/2Nb1/2O3- xPbTiO3 system at x ≈ 0.1 have been ascribed previously to the change of the lattice symmetry from rhombohedral to tetragonal or to the decrease of the lattice parameter with x. We carried out structural, dielectric, magnetization, and Mossbauer studies of (1-x)PbFe1/2Nb1/2O3-xPbZrO3 system, where the symmetry remains rhombohedral, while the lattice parameter increases with x. However, the magnetic x,T-phase diagram of (1-x)PbFe1/2Nb1/2O3-xPbZrO3 appeared to be very similar to that of (1-x) PbFe1/2Nb1/2O3-xPbTiO3. Anomalies of composition dependence of magnetic phase transition temperatures at x ≈ 0.1 are supposed …
Raman Studies of Structural Phase Transitions in Perovskite Ferroelectric Sodium Niobate Solid Solutions
2008
Raman spectra are sensitive to interactions between structural units and, consequently, may reflect fine rearrangements of the units of cation sublattice occuring at compositional changes affecting the phase equlibrium and ferroelectric properties of the crystal. Obtaining Raman spectra show the information on disordering of structural units depending on composition of the cation sublattice in real Li x Na 1 − x Ta y Nb 1 − y O 3 ferroelectrics. On the basis of experimental studies shown, that not only the frequency but also intensity of some “rigid” bands may serve as the function of order parameter of phase transition in Landau's theory of the second order phase transition.
Structure and properties of high piezoelectric coupling Pb(B′½Nb½)O3-PbTiO3binary systems
1999
Abstract The (1-x)Pb(Lu½ Nb½)O3-xPbTiO3 and (1-x)Pb(Er½ Nb½)O3-xPbTiO3 binary systems have been obtained, the structure and properties of which are studied. The unit cell of erbium niobate (PErN) is described as pseudomonoclinic of orthorhombic Bmm2 symmetry: a=c=4.2161 A b=4.0869 A β=90.55° and composition is characterized with antiferroelectric phase transition at 305°C. The PErNT system has the morphotropic phase region extending over the x=0.4–0.6 interval. In PLuNT ceramics system the pseudomonoclinic phase structure Bmm2 extending over the 0≤x ≤0.38 interval becomes pseudocubic at x≈ 0.2. The morphotropic region is spread over 0.38< × < 0.49; at higher PT concentrations (1.0 ≥ × ≥ 0.4…
Quantum chemical modelling of perovskite solid solutions
2000
In line with our previous study (Eglitis R I et al 1998 J. Phys.: Condens. Matter 10 6271) for a single Nb impurity and Nb clusters in KTaO3 we present here the results of calculations for a series of perovskite KNbx Ta 1−x O3 (KTN) solid solutions (x = 0, 0.125, 0.25, 0.75, and 1). The quantum chemical method of the intermediate neglect of the differential overlap (INDO) combined with the large unit cell (LUC) periodic model is used. According to the INDO calculations, Nb impurity becomes off-centre in KTaO3 already at the lowest studied Nb concentration. Its off-centre displacement is in a good agreement with XAFS measurements. We compare our results with previous FP-LMTO calculations. Pe…
Vibrational Analysis of Paraelectric–Ferroelectric Transition of LiNbO3: An Ab-Initio Quantum Mechanical Treatment
2021
FSG acknowledges the CINECA award under the ISCRA initiative (HP10BJO47B) for the availability of high-performance computing resources and support.