Search results for "ELECTRICITY"
showing 10 items of 1225 documents
Theoretical investigation of the platinum substrate influence on BaTiO 3 thin film polarisation
2019
Density functional theory calculations are performed to study the out-of-plane polarisation in BaTiO3 (BTO) thin films epitaxially grown on platinum. Prior to any polarisation calculation, the stability of the Pt(001)/BaTiO3(001) structure is thoroughly discussed. In particular, the nature of the Pt/BTO and BTO/vacuum interfaces is characterised. The growth of BTO is shown to start with a TiO2 layer while the nature of the surface termination does not broadly modify the stability. Therefore both upper terminations are considered when describing the ferroelectric behaviour in Pt/BTO interfaces. The geometric and electronic effects of the substrate on the polarisation are investigated. To iso…
Influence of Structure Ordering, Defects and External Conditions on Properties of Ferroelectric Perovskites
2000
Results of comprehensive studies of the (A’A“)(B’B”)O3-ferroelectric perovskites are reported. Examined compositions include Pb1-xLax(Zr0.65Ti0.35)1-x/4O3(PLZT), PbSc0.5Nb0.5O3(PSN), PbSc0.5Ta0.5O3(PST), and PMNT, PSNT and PLuNT pseudo-binary systems exhibiting pronounced dielectric, electrooptical, and electromechanical properties. Degree of ordering in the materials has been varied by chemical composition (modification, isomorphic ion substitution), by variation of technology (hot-pressing, specific thermal treatment, thin films), and by irradiation of different kind and intensity (γ-rays, electrons, neutrons).
Dielectric relaxation of space charges and polarons in ferroelectric perovskites
2001
Abstract In all ferroelectric perovskites, intentionally introduced or “unwanted” point defects do play a role in the dielectric spectra and in the conductivity. Above room temperature, space charge relaxation at the electrodes interfaces are observed. This can be of interest in the context of the nowadays applications of ferroelectric thin films. At liquid helium temperatures much more localised dielectric relaxation occurs. Special emphasis will be brought on SrTiO3 which has received renewed interest at the beginning of the nineties and for which a wealth of reliable experimental data are available. Considering that a gradual freezing of polarized objects is occurring at low temperatures…
Antiferroelectric PbZrO3 thin films: structure, properties and irradiation effects
2004
Abstract Irradiation effects on highly oriented antiferroelectric PbZrO 3 and ferroelectric Pb 0.92 La 0.08 (Zr 0.65 Ti 0.35 )O 3 thin films are investigated being exposed to neutron irradiation up to fluence 2*10 22 m −2 . The higher resistance of antiferroelectric PbZrO 3 thin films as compared to ferroelectric heterostructures to large fluences of neutron irradiation is recognized and discussed. Influence of two factors (structural and charge) was taken into account analysing irradiation effects on materials of different polarization states: ferroelectric PLZT (ceramics and thin films) and antiferroelectric PbZrO 3 films.
Nonresonant hole burning spectroscopy of the relaxor ferroelectric PLZT
2002
Abstract The polydispersive dielectric response of a lanthanum-modified lead zirconate titanate relaxor ferroelectric was studied using nonresonant hole burning (NHB) spectroscopy. The dynamic heterogeneity of this material was evidenced by the fact that it was possible to burn frequency-dependent spectral holes. The maximum position of the spectral holes depended on the square root of the pump frequency Ω . The refilling of the spectral holes was monitored subsequent to excitation using various pump frequencies. The refilling data could be collapsed onto a master curve by re-scaling them, again, using Ω −0.5 as scaling factor. The refilling time was found to be much longer than the time sc…
Spin Logical and Memory Device Based on the Nonvolatile Ferroelectric Control of the Perpendicular Magnetic Anisotropy in PbZr 0.2 Ti 0.8 O 3 /Co/Pt …
2020
Elastic and piezoelectric properties of BaTiO3 at room temperature
1999
Abstract We have calculated the phonon dispersion curves of barium titanate (BaTiO 3 ) at room temperature. A lattice dynamical formalism using the shell model is used. This microscopic model includes the short-range interactions of axially symmetric type and the long-range Coulomb interactions and taking into account the electronic polarizability of constituent ions. Zone center phonon and a few phonons in the first Brillouin zone are used for fitting. The values of relevant parameters are critically analyzed. A calculation of the elastic and piezoelectric properties is presented and compared with the available experimental data.
Soft mode in PMN–PSN ceramics
2008
Various ordered and disordered (1–x)Pb(Mg1/3Nb2/3)O3 –x Pb(Sc1/2Nb1/2)O3 (PMN–PSN) ceramics were studied by THz transmission spectroscopy in the temperature range of 10–300 K. It is found that the dielectric relaxation dominates in the spectra in higher temperatures, T > 170 K. In contrast, below 150 K, the strength of relaxation becomes so weak that the phonon contribution can be separated. The phonon contributribution in the investigated frequency range (200 GHz–2 THz) is presumably caused by the E component of the Last mode. The component exhibits hardening on cooling in all investigated ceramics and its critical temperature in ferroelectric PMN–PSN ceramics (x = 1, 0.95) is lower than t…
Ferroelectricity and structure of BaTiO grown on YBa Cu O thin films
2000
We have investigated the crystal structure and the ferroelectric properties of BaTiO3 thin films with YBa2Cu3O \(_{7 - \delta }\) as the bottom and Au as the top electrode. Epitaxial heterostructures of YBa2Cu3O \(_{7 - \delta }\) and BaTiO3 were prepared by dc and rf sputtering, respectively. The crystal structure of the films was characterised by X-ray diffraction. The ferroelectric behaviour of the BaTiO3 films was confirmed by hysteresis loop measurements using a Sawyer Tower circuit. We obtain a coercive field of 30 kV/cm and a remanent polarisation of 1.25 μC/cm2. At sub-switching fields the capacitance of the films obeys a relation analogous to the Rayleigh law. This behaviour indica…
Broad Distribution of Relaxation Times in 0.6PMN-0.4PZN Relaxor Ceramics
2007
In this paper dielectric spectra of 0.6PMN-0.4PZN ceramic obtained from broadband dielectric spectroscopy is presented. Measurements revealed an unusual relaxor like nature. Two different processes in the dielectric spectra have been observed. High frequency, or short relaxation times, behaviour is typical for ferroelectric crystals. Longest relaxation times do not follow Vogel—Fulcher dependence, which is unusual for relaxors.