Home OALib Journal OALib PrePrints Submit Ranking News My Lib FAQ About Us Follow Us+
 Title Keywords Abstract Author All
Search Results: 1 - 10 of 100 matches for " "
 Page 1 /100 Display every page 5 10 20 Item
 Physics , 2007, Abstract: Piezoelectric PZT solid solutions were studied as a function of pressure and temperature. Moderate pressure is found to induce phase transitions to monoclinic phases (Cm,Cc) for Ti-rich PZT, which are the same ferroelectric phases responsible for the high piezoelectric properties of the MPB. The following transformation sequence P4mm -> Cm -> Cc -> F1 -> F-1 was identified upon increasing pressure. Compression behaviour is dominated by: (1) a rotation and a reduction of the spontaneouspolarization and (2) octahedral tilting leading to unit cell doubling. Future studies as a function of pressure, temperature and electric field on single crystals of heterovalent relaxor ferroelectric isotypes of PZT are proposed in order to better understand these potentially technologically-important piezoferroelectric materials.
 Yuri Mnyukh Physics , 2011, Abstract: It is demonstrated by analyzing real examples that phase transitions in layered crystals occur like all other solid-state phase transitions by nucleation and crystal growth, but have a specific morphology. There the nucleation is epitaxial, resulting in the rigorous orientation relationship between the polymorphs, such that the direction of molecular layers are preserved. The detailed molecular mechanism of these phase transitions and formation of the laminar domain structures are described and related to the nature of ferroelectrics.
 Physics , 2013, Abstract: In this paper, electrical properties of BaTiO3 nano crystals have been studied, Barium Titanate Nano Crystals are made by mechanical alloying method in a ball mill of SPEX 8000. In order to find Curie temperature, dielectric constant variation via temperature and hysteresis loops are investigated. Our results show that, there is a relationship between the time of milling and the curie temperature .this means with increasing milling time, grain size will decrease, consequently the curie temperature will decrease. In addition, with increasing temperature up to the Curie temperature, the hysteresis loop of samples decrease and at the Curie temperature the hysteresis loop changes to a straight line.
 物理学报 , 1996, Abstract: In this paper, the Merten' s equation and dispersion relation of polaritons in the uniaxial crystal had been deduced from the generalized dispersion relation of the phonon-polariton. Raman spectra of every LO, TO mode and oblique phonons in BaTiO3 and Ce: BaTiO3 single crystals have been recorded, the directional dispersion curves are fitted on the basis of Merten's equation. Raman spectra of A1 polaritons with different wave-vector q have been measured and the high and low frequency dielectric constants in both BaTiO3 and Ce:BaTiO3 are calculated. Two broad asymmetry bands in A1(TO) Raman spectra and the mechanics of structure phase transition in BaTiO3 are also discussed. The influence of Ce on the structure of BaTiO3 single crystal are analysed.
 Peter Galenko Physics , 2007, DOI: 10.1103/PhysRevE.76.031606 Abstract: Numerous experimental data on the rapid solidification of binary systems exhibit the formation of metastable solid phases with the initial (nominal) chemical composition. This fact is explained by complete solute trapping leading to diffusionless (chemically partitionless) solidification at a finite growth velocity of crystals. Special attention is paid to developing a model of rapid solidification which describes a transition from chemically partitioned to diffusionless growth of crystals. Analytical treatments lead to the condition for complete solute trapping which directly follows from the analysis of the solute diffusion around the solid-liquid interface and atomic attachment and detachment at the interface. The resulting equations for the flux balance at the interface take into account two kinetic parameters: diffusion speed $V_{DI}$ on the interface and diffusion speed $V_D$ in bulk phases. The model describes experimental data on nonequilibrium solute partitioning in solidification of Si-As alloys [M.J. Aziz et al., J. Cryst. Growth {\bf 148}, 172 (1995); Acta Mater. {\bf 48}, 4797 (2000)] for the whole range of solidification velocity investigated.
 中国物理 B , 1996, Abstract: We report the observations of the decay processes of light-induced absorption in one undoped and two Ce-doped BaTiO3 crystals. Two decay times were found, they had not a strong dependence on intensity in our experiment. We present a model with two different shallow trap centers to explain the experimental results. The theoretical and experimental resales agree well with each other. The light-induced absorption coefficients and decay times corresponding to the two shallow levels are also given.
 Hui Zhang Physics , 2012, DOI: 10.1063/1.4804151 Abstract: We have proposed the polarization rotation theory to understand the underlying physics of the large piezoelectric effect in ferroelectric crystals by referring to the coherent rotation model in ferromagnetism. When both the electric field energy and crystalline anisotropy energy are taken into account, the polarization in BaTiO3 crystal can be rotated toward the field direction. The numerical results have indicated the highly anisotropic polarization rotations and the field-induced-phases with different symmetries in the crystal. This theory is helpful for understanding the polarization reversal and the electromechanical effect in ferroelectric materials.
 Physics , 2007, DOI: 10.1103/PhysRevB.75.224116 Abstract: We develop a phenomenological thermodynamic theory of ferroelectric BaTiO3 (BT) thin films epitaxially grown on cubic substrates using the Landau-Devonshire eight-order potential. The constructed "misfit-temperature" phase diagram is asymmetrical. We found that, overall view of the phase diagram depends on the values of compliances used in calculations and provide two qualitatively different diagrams. A thermodynamic path for BT film grown onto particular substrate can be found using a plot of the room-temperature tetragonal distortion (c-a)/a as a function of misfit strain.
 Physics , 2007, DOI: 10.1142/S0129055X08003353 Abstract: A unified theory of phase transitions and quantum effects in quantum anharmonic crystals is presented. In its framework, the relationship between these two phenomena is analyzed. The theory is based on the representation of the model Gibbs states in terms of path measures (Euclidean Gibbs measures). It covers the case of crystals without translation invariance, as well as the case of asymmetric anharmonic potentials. The results obtained are compared with those known in the literature.
 金属学报 , 2008, Abstract: Effects of humidity on domain switching behaviors in BaTiO3 single crystals under electric field were investigated by polarized light microscopy (PLM). It was found that the humidity has different effect on different domain configurations. The low humidity has no effect on both a-b domain configuration and b-c domain configuration under fields. However, the high humidity can promote b domain switch to c domain under electric fields. The effects were explained by different adsorption of polar H2O molecules on different domain areas in humidity conditions.
 Page 1 /100 Display every page 5 10 20 Item