A CCD multi-channel spectroscopic instrument was used to measure the spectrum signal of the arc plasma, and the multi-wavelength spectrum for Ag/LaFe1-xNixO3-delta contact was obtained. Using this Spectroscopy diagnostics, the influences of the input power, the frequency and the gap of contact on arc plasma were investigated. The best work condition for Ag/LaFe1-xNixO3-delta contact material was found. The results will provide the testing of the contact material performances with an effective diagnostics way.

The ab initio calculation and bond valence model (BVM) are employed to investigate dopant occupancy in the Ti-doped high-temperature phase Ta2O5. In this structure, there are two types of Ta atoms, which the authors denote as Ta1 locating inside oxygen octahedral and Ta2 locating inside oxygen decahedral. The 5d state electron configuration of Ta1 and Ta2 is different, the hybridization between Ta1 5d state and O 2p state is stronger than that between Ta2 and O. The chemical bonding between Ta and oxygen ions is mainly covalent. However, there is an increase of the covalent character in going from Ta1–O bond to Ta2–O bond. Both total energy method and BVM indicate that Ti substituting Ta1 is energy favorable, and this maybe due to different electronic structures of Ta1 and Ta2.

Electronic and structural properties of Nb-doped SrTiO3 are studied using the first principles density functional theory (DFT) calculations based on a plane–wave basis and pseudopotentials. Dopant formation energy, structure distortion, band structure as well as density of states have been obtained. Dopant formation energy results show that Nb preferentially enters the Ti site in SrTiO3, which is good agreement with experimental observations. The Fermi level of the Nb-doped SrTiO3 move into the bottom of conduction band, and the system undergoes an insulator-to-metal transition. Due to the appearance of the carrier impurity from Nb doping, there is a significant distortion on the top valence band.

Lead-free piezoelectric (Bi0.95Na0.75K0.20-xLix)(0.5)Ba0.05TiO3 ceramics have been prepared by conventional process for different lithium substitutions. The SEM images show that the ceramics are well sintered at 1428 K. Dielectric and ferroelectric measurements have been performed. With the increasing of lithium substitution, the Curie temperature of the (Bi0.95Na0.75K0.20-xLix)(0.5)Ba0.05TiO3 ceramics shifts from 570 K to 620 K, but the maximum value of the dielectric constant decreases from 6700 to 4700 correspondingly. A relatively larger remanent polarization of 36.8 mu C/cm(2) has been found in the x=0.05 sample. The coercive field decreases as the lithium substitution amount increases. An optimized d(33)=194 x 10(-12) C/N and a relative dielectric constant epsilon(r)=1510 have been obtained in (Bi0.95Na0.75K0.15Li0.05)(0.5) Ba0.05TiO3. (C) 2006 Elsevier B.V. All rights reserved.

The shape of hysteresis loop as well as domain pattern of ferroelectric during polarization reversal process has been simulated using Monte Carlo method on Ising model. Apart from the nearest-neighboring exchange interaction in the Ising model, we take into the contributions of the third-neighboring interactions and the four-body couplings. The simulation is carried out on a two-dimension square 200 x 200 lattice with Metropolis sampling. A sinusoidal electric field is applied to reverse the polarization to get the hysteresis loop and domain patterns. At low temperature, the hysteresis loop shows a typical ferroelectric feature. When the temperature increases, pinched hysteresis loops have been obtained. By checking the domain patterns during the reversal process, we found that the domain pattern is firstly switched from a ferroelectric state into a mixed ferroelectric and antiferroelectric states, then to the ferroelectric phase at last. The interesting point in this model is that there is no conventional negative interaction in the Hamiltonian, but a combination of positive non-nearest-neighboring coupling and multi-body coupling. Also this kind of hysteresis loop is quite similar to that observed in sodium bismuth titanate systems experimentally.

The lattice distortion strain induced ferroelectricity in SrZrO3/SrTiO3 superlattice is studied using first principles density functional theory. Within the tetragonal symmetry P4mm, the lattice distortion from the lattice mismatch in the superlattice structure is determined through energy minimization. This kind of lattice distortion leads to the formation of spontaneous polarization in the superlattice, although neither SrZrO3 nor SrTiO3 is ferroelectric. From analysis of the relative displacements of the cations and anions, we have found that the SrZrO3 cell may make a greater contribution to the polarization in the SrZrO3/SrTiO3 superlattice than the SrTiO3 cell. An extremely large polarization of 42.7 mu C/cm(2) has been predicted. (c) 2006 Elsevier Ltd. All rights reserved.

The pseudopotential methods have been employed to investigate the electronic structures of alpha and beta-phase poly (vinylidene fluoride). In the energy band structure of beta-phase PVDF, a large dispersion of the valence band is found only along the chain direction, which agrees well with the angle-resolved photoemission experiments and implies the quasi-one-dimensional nature of beta-phase PVDF. The large dispersion of the LUOM is caused by H s, C-2 s p state mainly. The energy band structure of beta-phase exhibits anisotropy, while isotropy is found in the energy band of alpha-phase PVDF.

ABSTRACT The pseudopotential methods have been employed to investigate the electronic structures of α and β-PHASE poly (vinylidene fluoride). In the energy band structure of β-PHASE PVDF, a large dispersion of the valence band is found only along the chain direction, which agrees well with the angle-resolved photoemission experiments and implies the quasi-one-dimensional nature of β-PHASE PVDF. The large dispersion of the LUOM is caused by H s, C2 s p state mainly. The energy band structure of β-PHASE exhibits anisotropy, while isotropy is found in the energy band of α -phase PVDF.

ABSTRACT A modified diffused limited aggregation model (mDLA) and Ising model has been proposed on a two dimension 200 × 100 lattice for investigating the physical property in a fatigued ferroelctric thin film. Firstly mDLA is used to generate the dendritic pattern. Then a spin-1/2 Ising model is implemented in the lattice to represent the dipole array in the films. Monte Carlo method has been employed in the simulations. Domain patterns as well as hysteresis loop have been obtained. It was found that the polarization could be easily reversed around the dendrite sites, which leads to a chopped shoulder in the hysteresis loop.

We perform density functional theory method to study the electronic structure of relaxor feffoelectrics Pb(Mg1/3Nb2/3)O-3. An ordered perovskite structure based supercell was examined with the B sites Nb-Mg-Nb stacking along the [001] direction. Band structure, density of states and electron density have been obtained. The calculated band gap is a direct one with the value of 1.05 eV. It is found that the Mg-O bond presents no covalency, whereas there is a considerable Nb-O covalent bonding. The different B-O bonding characters might be responsible for the relax or properties of Pb(MG(1/3)Nb(2/3))O-3 crystal.