Yang Feng-Xia

The influence of ferroelectric KTN particles on electric properties of 0–3 ferroelectric composites

A triphasic ferroelectric composite is obtained when ferroelectric potassium tantalate niobate particles [KTN] with a high dielectric constant and electric conductivity are embedded in a traditional 0–3 manganese and niobate modified lead zirconate titanate [PMNZT]/polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] copolymer biphasic-ferroelectric composite. The electric properties are studied for the ferroelectric composite in which the volume fraction of KTN particles is in the range 0%–24% and KTN is a passive phase. The experimental data show that the volume fraction of KTN particles strongly influence the electric properties of ferroelectric composite, and that the triphasic composite doped with KTN has higher ferroelectric, piezoelectric and pyroelectric properties than the biphasic composite with the same PMNZT volume fraction.

Effect of pulse width and fluence of femtosecond laser on electron-phonon relaxation time

The electron phonon relaxation time as functions of pulse width and fluence of femtosecond laser is studied based on the two-temperature model. The two-temperature model is solved using a finite difference method for copper target. The temperature distribution of the electron and the lattice along with space and time for a certain laser fluence is presented. The time-dependence of lattice and electron temperature of the surface for different pulse width and different laser fluence are also performed, respectively. Moreover, the variation of heat-affected zone per pulse with laser fluence is obtained. The satisfactory agreement between our numerical results and experimental data indicates that the electron phonon relaxation time is reasonably accurate with the influences of pulse width and fluence of femtosecond laser.

Global Pressure of One-Dimensional Polydisperse Granular Gases Driven by Gaussian White Noise

We study the global pressure of a one-dimensional polydisperse granular gases system for the first time, in which the size distribution of particles has the fractal characteristic and the inhomogeneity is described by a fractal dimension D. The particles are driven by Gaussian white noise and subject to inelastic mutual collisions. We define the global pressure P of the system as the impulse transferred across a surface in a unit of time, which has two contributions, one from the translational motion of particles and the other from the collisions. Explicit expression for the global pressure in the steady state is derived. By molecular dynamics simulations, we investigate how the inelasticity of collisions and the inhomogeneity of the particles influence the global pressure. The simulation results indicate that the restitution coefficient e and the fractal dimension D have significant effect on the pressure.

Collision Statistics of Driven Polydisperse Granular Gases

We present a dynamical model of two-dimensional polydisperse granular gases with fractal size distribution, in which the disks are subject to inelastic mutual collisions and driven by standard white noise. The inhomogeneity of the disk size distribution can be measured by a fractal dimension df. By Monte Carlo simulations, we have mainly investigated the effect of the inhomogeneity on the statistical properties of the system in the same inelasticity case. Some novel results are found that the average energy of the system decays exponentially with a tendency to achieve a stable asymptotic value, and the system finally reaches a nonequilibrium steady state after a long evolution time. Furthermore, the inhomogeneity has great influence on the steady-state statistical properties. With the increase of the fractal dimension df, the distributions of path lengths and free times between collisions deviate more obviously from expected theoretical forms for elastic spheres and have an overpopulation of short distances and time bins. The collision rate increases with df, but it is independent of time. Meanwhile, the velocity distribution deviates more strongly from the Gaussian one, but does not demonstrate any apparent universal behavior.

Quasi-Random Resistor Network Model for Linear Magnetoresistance of Metal–Semiconductor Composite

A new model for the linear magentoresistance (MR) of the Ag2+δSe and Ag2+δTe thin films is proposed. The thin him is considered as a metal-semiconductor composite and dispersed into an N – N quasi-random resistor network. The network is constructed from four-terminal resistors and the mobility of carries μ within the network has a quasi-random distribution, i.e. a Gaussian distribution with two constraint conditions. The model predicts that the MR increases with the increasing magnetic fields, and increases linearly at high field. Moreover, the MR decreases with the increasing temperatures. A good agreement between the theoretical MR and the available experimental data is found.

KTa0.4Nb0.6O3 nanoparticles synthesized through solvothermal method

Potassium tantalate niobate (KTa0.4Nb0.6O3, KTN) nanoparticles of perovskite structure were successsfully synthesized by a solvothermal method. The KTN nanoparticles synthesized at 250 °C for 8 h with 1 to 4 M KOH concentration using isopropyl alcohol [(CH3)2 CHOH] as the solvent was composed of a single phase of cubic perovskite structure. Futhermore, the KTN powers synthesized at the same conditions besides of using (CH3)2CHOH/H2O as a solvent compose of a single phase of tetragonal perovskite structure. The nanoparticles exhibit a mixture of cubic and prism-like shapes with lengths of 100 nm to 500 nm and average cross sections of 200×200 nm2. The solvent dependence of the powder formation is discussed. X-ray diffraction and electron diffraction results show that the powders have the needed tetragonal perovskite structure. The band gap of KTN nanoparticles is determined to be 3.26 eV from the optical absorption spectra.

Dielectric Properties and Lattice Distortion in Rhombohedral Phase Region and Phase Coexistence Region of PZT Ceramics

In this paper, the relation between the dielectric properties and the lattice distortion in the phase coexistence region is discussed using a phase statistical distribution model, and in the rhombohedral phase region the two connection equations on the dielectric properties and the lattice distortion are established. Particularly, the relation between the dielectric properties and the lattice distortion is investigated in the phase coexistence region of PZT ceramics, and the fitting value of the volume fraction of the tetragonal phase VT to composition x in the equation is determined. Further, the fitting results are well consistent with the related experimental data. It involves more profound physical process than relation between the dielectric properties and composition x.