Search results for "Electricity"
showing 10 items of 1225 documents
Influence of Lithium Substitution on Structure, Electric and Pyroelectric Properties of Sodium Niobate Ceramics
2012
Li0.02Na0.98NbO3 ceramics were prepared by a conventional method. A single-phase perovskite structure was identified by an X-ray diffraction method. The SEM and EDS studies revealed that the Li0.02Na0.98NbO3 samples were perfectly sintered and chemically homogeneous. Electric measurements showed that Li0.02Na0.98NbO3 was sensitive to the frequency of the applied electric field and revealed that the ac conductivity changed with frequency according to the formula: σ(ω) = σdc +Aωn where n < 1. These results were discussed with a reference to the conduction mechanism as a type of polaron hopping.
Ferroelectric domains in BaTiO3powders and ceramics evidenced by X-ray diffraction
1995
Abstract Through three different studies, using BaTiO3 samples, as a powder while heating over the Curie temperature, and as a ceramic while applying an electric field, it is shown how X-ray diffraction (XRD) is able to give information about the evolution of the ferroelectric domain microstructure. Firstly, the relative intensities of the 002 and 200 lines, as a function of the applied electric field, exhibit the motion of the 90[ddot] domain walls. However, XRD is unable to provide any distinction between two 180[ddot] domains. Secondly, the profile of those two lines and of the other double (hhl), (lhh) lines is particular: the unusual diffracted intensity between such double lines has t…
Fine grain barium titanate: ferroelectric domains and X-ray diffraction diagram
2002
Through three different studies using various kinds of BaTiO/sub 3/ samples: as a powder while heating over the Curie temperature; as a green ceramic as a function of the forming pressure; as a ceramic while applying a D.C. field. It is shown how X-ray diffraction is able to give information about the evolution of the 90/spl deg/ ferroelectric domain microstructure.
Static and dynamic properties of low-temperature order in the one-dimensional semiconductor(NbSe4)3I
2016
We investigated static and dynamic lattice properties in a quasi-one-dimensional charge-ordered semiconductor ${({\mathrm{NbSe}}_{4})}_{3}\mathrm{I}$ by using Raman, femtosecond pump-probe spectroscopy and x-ray diffraction. In addition to a well-documented pseudo-Jahn-Teller ferrodistortive structural transition at ${T}_{C}=274$ K, where the displacements of Nb ions lead to ferroelectric (FE) in-chain polarization with opposite direction in adjacent chains, all methods suggest an additional lowering of symmetry at ${T}^{*}\ensuremath{\approx}160$ K. Although antiferroelectric (AFE) phase is partially formed at ${T}_{C}$, our results consistently point to an enhancement of the interchain or…
X-Ray diffraction diagram evolution of a BaTiO3ceramic under an electric field
1994
Abstract The X-ray diffraction diagrams of a coarse grained pure BaTiO3 ceramic have been recorded as a function of the applied electric D.C. field. This field was perpendicular to the X-ray incoming surface. The experimental device used allows to record diffraction diagrams while the electric field step by step increases. The intensity ratio of the 002 line over the 200 line increases with the applied electric field. The evolution of the X-ray diffraction line intensities is in correlation with the first polarization curve of the ferroelectric ceramic. These results evidence a contribution of the 90° ferroelectric domains pattern to the X-ray diffraction diagram of BaTiO3.
The Effects of Thermo-Baric Synthesis on the Structure and Properties of the Ferroelectric Li0.125Na0.875NbO3Solid Solution
2014
ABSTRACTResults of X-ray diffraction, dielectric, and Raman studies of the ferroelectric Li0.125Na0.875NbO3 solid solution obtained under hot-pressing conditions (6 GPa, 1400 and 1800 K) are compared with those of the same compound synthesized by conventional ceramics technology. The thermo-barometric synthesis is found to improve the ordering of cations and to increase the value of dielectric permittivity and ion conductivity of the ceramics.
Ferroelectric Domain Walls in BaTiO3: Fingerprints in XRPD Diagrams and Quantitative HRTEM Image Analysis
1997
The structure of ferroelectric domain walls in BaTiO3 has been investigated through two complementary approaches, a global one by the fine analysis of X-ray diffraction patterns, the other essentially local via a quantitative image analysis method developed and applied to High Resolution Transmission Electron Microscopy images. These two original approaches converge towards a clear description of 90○ walls which are shown to be a 4–6 nm wide region where the crystallographic discontinuity is accommodated by irregular atomic displacements. The results given here demonstrate that the usual structural theoretical description of walls commonly accepted for energy calculations are far too simpli…
SNOM study of ferroelectric domains in doped LiNbO3 crystals
2009
Abstract This work shows a study of the periodic ferroelectric domains formed in LiNbO3 crystals doped with rare earths by means of scanning near field optical microscopy (SNOM) technique. It has been observed periodic structures associated with ferroelectric domains with an unexpected high value of the optical contrast working under reflectance SNOM mode. From Raman-Nath diffraction patterns, a refractive index modulation of Δ n ∼ 1 0 − 4 has been calculated. These results were correlated with the ferroelectric periodic domains obtained by the SNOM technique. A light waveguide effects along the ferroelectric domains is suggested to explain the high reflectance contrast observed in SNOM exp…
Structural and electric characteristics of (Na0.5Bi0.5)0.50Ba0.50TiO3 and (Na0.5Bi0.5)0.20Ba0.80TiO3 ceramics
2003
Abstract (Na0.5Bi0.5)0.50Ba0.50TiO3 and (Na0.5Bi0.5)0.20Ba0.80TiO3 ceramics have been prepared by the solid state reaction and studied by X-ray diffraction and by measurements of dielectric and ferroelectric properties between room temperature and 550 °C. A sharp increase in the electric permittivity and dielectric loss near 212 °C (for the first material) and near 205 °C (for the second material) on heating with remarkable thermal hysteresis have been observed. This sharp increase in dielectric responses indicates transformation between normal and relaxor ferroelectric states. The X-ray diffraction study shows that this transformation corresponds to the first order phase transition from te…
Detection of morphotropic phase boundary in A-site/Ca-substituted Na0.5Bi0.5TiO3 complex oxides ferroelectric system
2020
Abstract Vibrational and structural properties of lead-free piezoelectric (1-x)Na0.5Bi0.5TiO3–xCaTiO3 (0 ≤ x ≤ 1.00) solid solutions have been investigated using Raman spectroscopy and X-ray diffraction. Different anomalies were detected and analyzed taking into consideration the phase transition from rhombohedral to orthorhombic phase at room temperature. All Raman bands were interpreted through the variation in the peak positions (frequency) and the corresponding half-widths at half maximum (HWHM) as a function of x. XRD used as a complementary technique to Raman spectroscopy, showed that the rhombohedral – orthorhombic phase transition went gradually through an intermediate phase consist…