Search results for "Titan"
showing 10 items of 1109 documents
Adjuvant Effect of Titanium Brushes in Peri-Implant Surgical Treatment: A Systematic Review
2021
Background: the prognosis of peri-implant surgery can be affected by poor decontamination of the implant surface, which could be improved with the use of titanium brushes. The objectives of this systematic review were to evaluate the effectiveness of titanium brushes in the decontamination of the implant surface in terms of plaque index, probing depth, bleeding on probing and bone loss/gain; as well as its effectiveness according to the type of peri-implant bone defect. Methods: an electronic search was carried out in the PubMed, Scopus, Cochrane and Embase databases, as well as a manual search. The search strategy included four keywords: “Peri-implantitis”, “Periimplantitis”, “Implant Surf…
Hydrothermal origin and age of jadeitites from Sierra del Convento Mélange (Eastern Cuba)
2012
Jadeitite (jadeite jade) from Sierra del Convento (eastern Cuba) occurs in a subduction-related serpentinite-matrix melange associated with a variety of high-pressure tectonic blocks including garnet-amphibolites and related anatectic trondhjemites. The eastern Cuban jadeitite is massive and characterized by rare quartz inclusions and omphacite exsolution in jadeite crystals, as well as replacement or infilling by omphacite. Minor minerals include epidote, biotite, albite, phengite, titanite, rutile, zircon, and apatite. Oscillatory zoning in jadeite crystals and zircon ages suggest hydrothermal crystallization in veins formed in serpentinized peridotite, probably of the mantle wedge. Al-Na…
Non-linear dielectric behaviour and glass phase in Sr1-xCaxTiO3(x= 0.002 andx= 0.003)
1999
This work reports a study of the temperature and electric field dependence of the dielectric constant of strontium calcium titanate. The first part of the paper is focused on the analysis of a mean-field model for the polar clusters generated by the random impurities of calcium. It is shown that the dipolar moments within each cluster can be represented by an equivalent quantum two-level system. General expressions for the temperature and field dependence of the Edward-Anderson order parameter and of the electrical polarization are given. Analytical solutions are also obtained in the limit of high temperatures and in the limit of high tunnelling frequencies. The second part of the work repo…
Substitution effects on the relaxor properties of lead magnesium niobate ceramics
1999
Abstract The temperature dependence of the dielectric permittivity is studied in different Pb(Mg⅓Nb⅔)O3 based ceramics, in which the ordered region size can be changed by introducing titanium or lanthanum ions. Both the relaxor behaviour and the nonlinear dielectric component are found to be dependent on the impurity content. Especially, the nonlinearity increases strongly as the material exhibits a more conventional ferroelectric behaviour, i.e. as the size of the polar clusters, which develop in the paraelectric matrix, increases.
Mean field behaviour of Sr1−xCaxTiO3
1996
A systematic analysis of the dielectric constant as a function of temperature in SrTiO 3 : Ca crystals with Ca content of 0.0020, 0.0032, 0.0055. 0.0058, and 0.0110 shows that the Barrett parameters are clearly modified by the Ca content. We have found for each Ca concentration the temperature below which the contribution of the Ca induced clusters becomes sizeable. The values obtained for the fitted parameters in the Barrett formula allow us to trace a boundary between the low-temperature quantum paraelectric and ferroelectric regimes.
Germanium modified BaTiO3as a promising electroceramics
2016
ABSTRACTThe polycrystalline sample of BaTi0.95Ge0.05O3 was prepared by solid-phase reaction using a conventional method. The morphology of investigated sample was characterised by scanning electron microscopy (SEM). The results allowed to determining the stoichiometry of the material and evaluate their microstructure. High quality samples were investigated, the grains are well shaped without of a glassy phase. The dielectric properties of the BaTi0.95Ge0.05O3 ceramics were determined. The results were compared with these ones obtained for pure BaTiO3. The obtained data indicated that the substitution of Ge+4 ions had an influence on the values of the real (ϵ′) and imaginary (ϵ″) parts of el…
Structural and in depth characterization of newly designed conducting/insulating TiN O /TiO2 multilayers obtained by one step LP-MOCVD growth
2001
Abstract TiNxOy/TiO2 multilayers have been grown by LP-MOCVD using titanium isopropoxide (TIP) precursor during the whole growth, but with an ammonia flow interrupted for the TiO2 layers. The one step growth process used to grow these structures allowed to stack the conducting and insulating layers without any growth breakdown. SIMS and TEM analyses showed the presence of an alternated insulating/conducting layers structure. Moreover, electrical measurements allowed to measure the dielectric part of insulating TiO2 stacked in these structures, whose permittivity was found to be about 80 for a MOS structure. Thus, such multilayers may lead to very promising applications in the microelectroni…
Semi-empirical indo and shell-model calculations for perovskites
1999
Abstract Structural, phonon and some elastic and dielectric properties have been calculated for various paraelectric or ferroelectric phases of the perovskites KNbO3 and SrTiO3, using either the semi-empirical INDO (Intermediate Neglect of Differential Overlap) method or a temperature-dependent shell model. The INDO method was used to calculate the energy changes resulting from [100], [110] or [111] displacements of Nb atoms in the cubic perovskite cell of KNbO3, at 0K. The conventional shell model gives a good account of the elastic, dielectric and phonon properties of the cubic phase of strontium titanate at room temperature, but difficulties remain in modelling the permittivity and elast…
Structural and Dielectric Properties of (Na0.5Bi0.5)0.70Ba0.30TiO3 Ceramics.
2003
Abstract A (Na0.5Bi0.5)0.70Ba0.30TiO3 ceramic has been studied by X-ray diffraction and by measurements of dielectric and ferroelectric properties between room temperature and 450 °C. A sharp increase in the electric permittivity and dielectric loss near 200 °C has been observed. This sharp increase in dielectric responses indicates a transformation between normal and relaxor ferroelectric states. It is found that polar regions can exist at higher temperatures. The X-ray diffraction study shows that the transformation corresponds to the first order phase transition from tetragonal to cubic. The use of the (Na0.5Bi0.5)0.70Ba0.30TiO3 ceramic for device application has also been indicated.
Bias Field Effect on Dielectric Response in the Region of Phase Transitions in (Pb,La)(Zr,Sn,Ti)O3Ceramics
2007
The dielectric response of (Pb 0.97 La 0.02 ) (Zr 0.53 Ti 0.12 Sn 0.35 )O 3 (PLZTS-2/53/12/35) ceramics was measured as a function of DC bias field E =. As the bias field intensity increases the values of ϵ′ max and ϵ” max are found to shift towards a lower temperature. A possible coexistence of the ferroelectric and antiferroelectric phases over a wide range of temperatures in the PLZTS-2/53/12/35 samples is assumed to explain the observed features of ϵ′ (T), ϵ” (T), and ϵ′ (E=) curves.