Search results for "Titanate"
showing 10 items of 131 documents
Water Splitting on Multifaceted SrTiO3 Nanocrystals: Computational Study
2021
The financial support of M-ERA.NET2 Sun2Chem project is greatly acknowledged by E.K. Authors thank Dr. Marjeta Ma?ek Kr?manc and prof. Chi-Sheng Wu, for the fruitful discussions. The financial support of FLAG-ERA JTC project To2Dox is acknowledged by Y.A.M. This paper is based upon the work from COST Action 18234, supported by COST (European Cooperation in Science and Technology). The support is greatly acknowledged by Y.A.M. and V.K. The grant No. 1.1.1.2/VIAA/l/16/147 (1.1.1.2/16/I/001) under the activity of Post-doctoral research aid is greatly acknowledged by M.S. and D.B. The Institute of Solid State Physics, University of Latvia (Latvia) as the Centre of Excellence has received fundin…
Synthesis and optical characterization of Er-doped bismuth titanate nanoparticles grown by sol-gel hydrothermal method
2017
Abstract The Er 3+ -doped bismuth titanate (Bi 4 Ti 3 O 12 , BIT) nanoparticles were synthesized by a combined sol–gel and hydrothermal method under a partial oxygen pressure of 30 bar. The composition and morphology were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman scattering. They showed pure and homogeneous spherical BIT nanoparticles with a size below the 30 nm. The incorporation of Er ions showed a strong decrease in the lattice parameters, as well as averaged particle size. The photoluminescence up-conversion (excitation wavelength =1480 nm) showed an enhancement of the infrared emission (980 nm) as Er concentration increased, achieving a maxi…
Iron oxides nanoparticles and titanate nanotubes dedicated to multimodal imaging and anticancer therapy
2013
The new implementations of nanoparticles in the medical field are one of the essential factors of the medical progress expected at the beginning of this XXIst century. Thus, the domain of the medical imaging is also affected by this technological evolution. This work consisted in developing theranostic probes with iron oxides nanoparticles (SPIO) and titanate nanotubes (TiONts) for multimodal imaging (magnetic/nuclear or magnetic/optical) and also possessing a therapeutic effect (hyperthermia/PDT or radiosensitization/PDT).The titanate nanotubes of this study have an average length of about 150 nm and were obtained by Kasuga's hydrothermal synthesis. These nanotubes present an outside diame…
Modeling of trapped charge effects in ferroelectrics: application to piezoactuators
1997
The strain response of lead zirconate titanate piezoelectric multilayer actuators have been measured up to 10 7 N/m 2 stress and the 3.10 6 V/m periodic unipolar driving voltage. An additional nonstationary strain component is detected. This effect is explained in terms of a simple solution of polarization kinetics specific for unipolar driving voltage. Preliminary experimentally assertions are given for space charge effects which manifest itself in the strain as well as charge plot after removing the mechanical load. It demonstrates that the static load free equilibrium of the actuator is not complete and the charge recently supported by the piezo voltage and then trapped forms a nonunifor…
Cobalt in strontium titanate based perovskites: preparation, characterization and role in the photocatalytic propene partial oxidation
2016
Strontium titanate perovskite (SrTiO3) and analogous materials in which Y partially substitutes Sr have been prepared as basis to integrate Co in the structure. The Co inserrtion has been performed by wet impregnation or coprecipitation methods. The obtained powders have been physico-chemically characterized and tested as photocatalysts in the propene partial oxidation by using a solar simulating reactor. Correlation between photocatalytic performance and physicochemical characteristics of the different catalysts allows to assess a key role of local nanostructuring of CoOx sites on the selectivity and distribution of products.
Ab initiothermodynamics ofBacSr(1−c)TiO3solid solutions
2005
Based on ab initio calculations for a number of the ${\mathrm{Ba}}_{\mathrm{c}}{\mathrm{Sr}}_{(1\ensuremath{-}\mathrm{c})}\mathrm{Ti}{\mathrm{O}}_{3}$ (BST) superlattices, we developed a thermodynamic approach to these solid solutions. In particular, we calculate the BST phase diagram and show that at relatively low temperatures (below $400\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $c=0.5$ and $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ for $c=0.1$) the spinodal decomposition of the solid solution occurs. As a result, we predict for small Ba concentrations formation of $\mathrm{Ba}\mathrm{Ti}{\mathrm{O}}_{3}$ nanoregions in a predominantly $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_{3}$ matrix and …
Atomistic simulation of SrTiO3 and BaTiO3 (110) surface relaxations
2000
Abstract The (110) surface relaxations were calculated for SrTiO 3 and BaTiO 3 perovskites in a cubic phase. Using a shell model, the positions of atoms in 16 near- surface layers placed atop a slab of rigid ions are calculated. The strong surface rumpling and induced surface dipole moments perpendicular to the surface are predicted for both the O-terminated and TiO-terminated surfaces.
Theoretical Simulations of Surface Relaxation for Perovskite Titanates
2000
The (100) and (110) surface relaxations are calculated for SrTiO3 and BaTiO3 perovskite thin films Using a semiempirical shell model, the positions of atoms in 16 near-surface layers placed atop a slab of rigid ions are calculated. Surface rumpling and surface-induced dipole moments perpendicular to the surface are calculated for different surface terminations. Surface relaxation is found much larger for the (110) surface. Our results for the (100) surfaces are compared with ab initio calculations and LEED experiments.
Structure and Phase Transitions in Nanocrystals
2007
• A size effect, or confinement effect. The nanograin behaves like a kind of box, within which the property may or may not exist [1]. Below a certain critical size, characteristics of the property depend on the grain size. This is the size or confinement effect. The way these characteristics change as a function of size is often non-monotonic and can exhibit extrema. • A surface or interface effect. In the nanograin, the contribution from layers close to the surface occupies a more and more important place in the overall behaviour of the material as the grain size decreases [1]. The surface energy gradually becomes the dominating contribution to the total energy of the material. Such a prop…
Preparation and characterization of sodium iron titanate ion exchanger and its application in heavy metal removal from waste waters.
2006
Abstract The ion exchange properties of sodium iron titanates, namely, NaFeTiO4, Na2Fe2Ti6O16 and iron-doped sodium nonatitanate were investigated. Conventional solid state and sol–gel methods were used in the synthesis of the sodium iron titanates. Structural characterization of the materials was performed with powder X-ray diffraction (XRD), thermogravimetry (TG), scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS) and with inductively coupled plasma optical emission spectrometry (ICP-OES). Based on TG analyses, the novel iron-doped sodium nonatitanate was proven to be a member of the layered titanate family. The different sodium iron titanates were compa…