Relaxation and transport mechanisms in (Pb.79La.21Ti.95)O3 ceramic

Variations of the dielectric constant and the relaxation time of La- doped PbTiO3 ceramic, as functions of frequency, are studied using the well- known model of Debye. The conductivity of the material is also studied and the variation of the activation energy as function of frequency is discussed.Variations of the dielectric constant and the relaxation time of La- doped PbTiO3 ceramic, as functions of frequency, are studied using the well- known model of Debye. The conductivity of the material is also studied and the variation of the activation energy as function of frequency is discussed

Calculating Bond-Stretching Force Constant of Binary Cubic Semiconductors and Ionic Materials Using a Simple Theoretical Approach

The vibrational dispersion relation of solid linear lattice of diatomic primitive cell, taking to account only the nearest-neighbor interaction between atoms, after generalizing it to become expressive of the three-dimensional one, was used to obtain a mathematical relation connecting the interatomic bond stretching force constant with the bulk modulus and the equilibrium lattice constant for ANB8-N binary semiconductors and binary ionic materials (monatomic ones automatically included).The analytical approach was supported by computer statistical adjustment, and the accuracy of the obtained mathematical formula was confirmed by comparing it with many values reported by other researchers with large number of materials of different groups, each of whom got a mathematical relation that differs from those of the others

Magnetic and spin waves studies in amorphous Gd 0.7 Y 0.3

In this paper, magnetic properties of amorphous Gd0.7 Y0.3 alloys have been studied using a linear dependence on H-1/2 of the saturation magnetization M(H); this dependence has been proved to be necessary for an adequate interpretation of magnetic behaviour of ferromagnetic amorphous compounds. Indeed, in a previous work, assuming a linear dependence on H-1 of M(H), magnetic parameters (magnetic moment, µGd , of Gd, mean exchange integral (J)) relevant to Gd0.7 Y0.3 have been undervalued. In the present work, these parameters, in addition to the stiffness constant, have been improved.In this paper, magnetic properties of amorphous Gd0.7 Y0.3 alloys have been studied using a linear dependence on H-1/2 of the saturation magnetization M(H); this dependence has been proved to be necessary for an adequate interpretation of magnetic behaviour of ferromagnetic amorphous compounds. Indeed, in a previous work, assuming a linear dependence on H-1 of M(H), magnetic parameters (magnetic moment, µGd , of Gd, mean exchange integral (J)) relevant to Gd0.7 Y0.3 have been undervalued. In the present work, these parameters, in addition to the stiffness constant, have been improved

Nonperturbative Analysis of the Harmonic Oscillator with a Time-Dependent Frequency

We apply the Floquet theorem and the resonating averages method to solve the Schrödinger equation of the harmonic oscillator whose frequency varies periodically with time. We determine its Floquet states and its corresponding wave functions. The formalism provides an efficiency tool for analyzing the various transition probabilities as well as the uncertainty relation of the system. The effect of a periodic external force on the Floquet states and the two-photon algebra realization are shortly discussed.We apply the Floquet theorem and the resonating averages method to solve the Schrödinger equation of the harmonic oscillator whose frequency varies periodically with time. We determine its Floquet states and its corresponding wave functions. The formalism provides an efficiency tool for analyzing the various transition probabilities as well as the uncertainty relation of the system. The effect of a periodic external force on the Floquet states and the two-photon algebra realization are shortly discussed

Numerical solutions of the Fokker Planck equation in the case of randomly oriented field acting on magnetic nanoparticles

The resolution of the Fokker-Planck equation (PFE) for the probability density of an assembly of fine particles, based on previous calculations, is extended to the case where the direction of the applied field has a random orientation. Using the PFE, Coffey et al. [6] have proposed a method of calculating the relaxation time τ, assuming H directed at an arbitrary angle ψ to the easy axis (H = H(ψ, φ=0)). In this report we will extend these calculations to the case where H = H(ψ, φ).The resolution of the Fokker-Planck equation (PFE) for the probability density of an assembly of fine particles, based on previous calculations, is extended to the case where the direction of the applied field has a random orientation. Using the PFE, Coffey et al. [6] have proposed a method of calculating the relaxation time τ, assuming H directed at an arbitrary angle ψ to the easy axis (H = H(ψ, φ=0)). In this report we will extend these calculations to the case where H = H(ψ, φ)

Random anisotropy studies in amorphous Fe80-x+x' Hox B20-x' alloys (0

In this paper, we have carried out a systematic study of the exchange and anisotropy effects on magnetic behavior of amorphous Fe80-x+x' Hox B20-x' (0<x<17; 0<x'<4) alloys. Primary analysis of magnetization data have led to the conclusion that the holmium magnetic structure is collinear. Exchange parameters, governing the magnetic ordering of our alloys, have been calculated from both mean field theory and high-field magnetization analyses. Study of the magnetization using the Chudnovsky's real space model has allowed us to determine the overall anisotropy constant, KL, from which we have determined, separately, the anisotropy energies for the iron and the holmium sublattices. Comparison of these two parameters to the exchange energies shows that the anisotropy to exchange ratio is small in these alloys.In this paper, we have carried out a systematic study of the exchange and anisotropy effects on magnetic behavior of amorphous Fe80-x+x' Hox B20-x' (0<x<17; 0<x'<4) alloys. Primary analysis of magnetization data have led to the conclusion that the holmium magnetic structure is collinear. Exchange parameters, governing the magnetic ordering of our alloys, have been calculated from both mean field theory and high-field magnetization analyses. Study of the magnetization using the Chudnovsky's real space model has allowed us to determine the overall anisotropy constant, KL, from which we have determined, separately, the anisotropy energies for the iron and the holmium sublattices. Comparison of these two parameters to the exchange energies shows that the anisotropy to exchange ratio is small in these alloys

Structure and Dielectric Properties of Cerium Doped Lead Titanate Ceramics

Sintered ceramic powders of cerium-doped lead titanate (Pbx/2+1CexTi1-xO3) ceramics with different Ce dopant concentration in the range (x=0-0.1) have been prepared using a sol-gel chemical route. The sol-gel technique is known to offer better purity and homogeneity, and can yield stoichiometric powders with improved properties at relatively lower processing temperature in comparison to conventional solid-state reaction. X-ray diffraction (XRD) scanning electronic microscope (SEM) and Raman spectroscopy studies have been carried out to identify the crystallographic structure and phase formation. The refinement of the structural parameters was carried out by the Rietveld method. PCT exhibit tetragonal symmetry with the perovskite structure. The dielectric properties as a function of frequency, and phase transition studies on sintered ceramics Pbx/2+1CexTi1-xO3 (x=0.03) has been investigated in detail over a wide temperature range 30-500°C and the results are discussed. Keywords:  A. ceramics; B. x-ray diffraction; C. Raman spectroscopy; D. dielectric; C. properties; E. Ce-modified

Effect of starting materials on the structure of pure and Gd-doped BaTiO3 elaborated by the sol gel process

Undoped and Gd-doped BaTiO3 samples, with the chemical formula BaGdxTi1-xO3-x/2□x/2, x = 0.00; 0.01; 0.02; 0.03; 0.04 and 0.05, were synthesized using the sol gel process. During the procedure of preparation of these samples acetic acid and distilled water were used as solvents. All the powders corresponding to the two series of undoped and doped samples were calcined in air at different temperatures and their crystalline phase was checked using results from XRD and Raman analyses. Acetic acid was shown to provoke the formation of the stable pseudo cubic structure for the two series of samples at relatively low temperature of crystallization, while with the use of distilled water only (without acetic acid) the tetragonal phase prevailed. In this study, the effect of acetic acid is discussed and the latter seems to play a more or less important role in the formation of the structure of BT material