Search results for "Titanate"

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.

Photorefractive detection of antiparallel ferroelectric domains in BaTiO 3 and BaTiO 3 :Co crystals

1998

An all-optical method involving one coherent beam of light and based on photorefractive wave mixing is used to reveal antiparallel ferroelectric domains in one pure, and two cobalt-doped, barium titanate crystals (BaTiO 3 ). Rod-shaped domains with square cross sections are revealed.

EPR studies of Mn, Fe, Co, and Cu doped PLZT and PMN compositions

1993

Results of Mn, Fe, Co, and Cu admixture EPR spectra studies in PLZT and PMN ceramics are discussed. The spectra of Mn, Fe, and Co ions with dominating absorption at geff = 2.0 and 4.3 are proposed due to d5 (S = 5/2) configurations (Mn2+, Fe3+, Co4+). The latter can be used as probes disclosing specific features (glass-like behaviour) of the structures. The Jahn-Teller ions (Mn3+, Fe4+, Co5+, Cu2+) are responsible for the dopant effect, e.g., the shift of the e(T) maximum to higher temperatures. The microscopic nature of differences of the dopant effect in PLZT and PMN materials and in the Mn Fe Co sequence is analyzed. [Russian Text Ignored].

Study of the Dielectric Properties of Europium Doped Barium Titanate Ceramics by an Impedance Spectroscopy

2015

The barium titanate (BaTiO3) and the BaTiO3 + 0.1wt.% Eu2O3 ceramics were prepared by a conventional ceramic method. The structural studies were carried out by means of an X-ray diffraction technique. The influence of the grains and the grain boundaries on the electrical properties was investigated using a impedance spectroscopy. This technique enables us to determine the values of grain and grain boundary resistance. The results show that the Eu doping leads to a significant reduction in the resistance value of the grains (˜105Ω) with respect to the pure BT ceramics (˜107Ω). The conductivity processes were determined from the Arrhenius behaviour of grain and grain boundary resistances.

Phthalocyanine–titanate nanotubes: a promising nanocarrier detectable by optical imaging in the so-called imaging window

2014

International audience; TiONts-phthalocyanine nanohybrids combining an efficient optical probe and a promising nanovector have been developed in a step-by-step approach and were thoroughly characterized. Each 150 nm long TiONts-Pc bear ca. 450 Pc. Three nanohybrids were prepared including three different linkers in quest for the best stability.

Energy leaks through the optical barrier created by H+ implantation in BaTiO3 and LiNbO3 planar waveguides

1998

Abstract The energy leaks through the index barrier created by the proton implantation process are put in evidence in planar optical waveguides made in BaTiO 3 and LiNbO 3 substrates. The selective detection of the light emerging from the guiding region permits to measure the optical attenuation of the guided wave. The results obtained on mono or twice implanted LiNbO 3 and BaTiO 3 waveguides are presented and discussed. It is shown that the light confinement is better in BaTiO 3 than in LiNbO 3 .

Two-wave mixing at 854 nm in BaTiO3:Rh planar waveguide implanted with He+

2001

Abstract Guided waves at 854 nm are observed in a BaTiO 3 :Rh waveguide fabricated by the technique of ion-beam implantation. The photorefractive interaction between two guided modes is demonstrated and characterized. The experiments reveal that the gain direction is reversed in the guiding layer in comparison with that in the bulk. A maximum gain of 24 cm −1 is achieved.

Dielectric and E.P.R. studies of Mn-doped barium titanate

1990

Manganese introduced in BaTiO3 as a substituant of titanium is able to trap the electrons produced during a sintering under a very low oxygen pressure. However it strongly modifies the vibrational ...

High Electromechanical Coupling in Relaxor Pb(Sc<sub>1/2</sub>Nb<sub>1/2</sub>) O<sub>3</sub> - PbTiO<sub>3…

1997

Comparative study of polar perovskite surfaces

2004

A novel model of the ‘‘zig–zag’’ (1 1 0) polar surface termination of ABO3 perovskites is suggested and analyzed. Classical shell model calculations for BaTiO3, SrTiO3 and LaMnO3 show that such the (1 · 2) (1 1 0) surface reconstruction has the lowest energy, comparable to that for the (1 0 0) surfaces. The calculated surface energy reaches the saturation only when 6–8 atomic near-surface planes are allowed to relax. Surface relaxation leads to the formation of considerable dipole moment perpendicular to the surface. The predicted surface polarization of thin perovskite films, even in the cubic phase, could affect their dielectric properties. � 2004 Elsevier B.V. All rights reserved.