Search results for "Zoe"

Grain size effect and local disorder in polycrystalline relaxors via scanning probe microscopy

2007

Local piezoresponse of individual grains in polycrystalline Pb0.9125La0.0975(Zr0.65Ti0.35)0.976O3 (PLZT 9.75/65/35) relaxor ceramics is studied using the scanning probe microscopy (SPM) technique. The observed piezoelectric contrast consisting of irregular (labyrinth-type) polarization patterns is attributed to the compositional disorder and consequent charge imbalance caused by high La concentration. A measure of this disorder, the polarization correlation length ξ, is directly determined using an autocorrelation analysis function implemented in the SPM software. The analysis of the obtained images shows that ξ taken at the scale ~200 nm varies as a function of the position inside the grai…

On Energy Harvesting Using Piezoelectric Transducer with Two-Port Model Under Force Excitation

2019

Piezoelectric (PE) materials are functional materials that can be used for transforming mechanical stress into electrical energy, that can then be stored and used for powering other devices. In this paper, we provide experimental investigation of PE transducers used for energy harvesting under external force-controlled excitation. The lumped parameter electromechanical model (LPEM) has been assumed and brought into a generalized two-port network notation. Laboratory experiments using a universal test machine (UTM) were performed and used for the parameter identification of the model. The two-port model formulation is validated by comparing results of numerical simulations and experimental d…

Harvesting rainfall energy by means of piezoelectric transducer

2013

In this paper a detailed study on the piezoelectric energy harvesting of rainfall is presented. Different features have been taken into account in order to define the limits in this energy harvesting. Only commercial transducers have been considered: a lead zirconate titanate and polyvinylidene difluoride transducer.

Study of the defects in La3Ta0.5Ga5.5O14 single crystals

2016

Abstract Defects that are formed during crystal growth pose a serious obstacle for potential application of La 3 Ga 5.5 Ta 0.5 O 14 (LGT) as a laser or piezoelectric crystal. We have performed the study of the defects origin in LGT crystals grown in different atmospheres using optical, EPR and time-resolved luminescence characterization methods. The absorption bands detected in the transparency region at 290, 360 and 490 nm ( T =300 K) demonstrate different dependence on crystal annealing in vacuum and air. EPR analysis demonstrated that the defects responsible for these bands are non-paramagnetic. X-ray irradiation results in hole trapping by oxygen ions thus forming O − centers perturbed …

Complete band gap in a pillar-based piezoelectric phononic crystal slab

2016

In this paper we have shown that it is possible to obtain the complete phononic band gaps in a square lattice of pillar-based phononic crystal. Bigger phononic band gap width can be obtained by increasing the height of pillar and it filling fraction, f. It is shown that the gap-to-mid-gap ratio of pillar at h/a = 0.5 has increased by 21.2% when it height increased to 1.25 and the gap-to-mid-gap ratio has increased by 12% when the filling fraction is increased from r/a = 0.3 to 0.45. The study also shows bigger band gap width and higher central frequency can be obtained by increasing the filling fraction of pillar.

Nonlocal model for a magneto-electro-elastic nanoplate

2013

A mathematical model based on nonlocal third-order shear deformation plate theory has been developed to evaluate the mechanical and electromagnetic behavior of magneto-electro-elastic nanoplates. Two types of magneto-electro-elastic composites have been considered, all of them combination of Barium Titanate sheets, that represents the piezoelectric phase, and Cobalt Ferrite, that is the piezomagnetic component. Setting magneto-electric boundary conditions on each laminate, it has been possible to extrapolate and to analyze free vibrations frequencies for all considered plates, allowing to do objective assessments on what factors influence laminate modes and, especially, how these vary in th…

Piezoelectric coefficients by molecular dynamics simulations in the constant stress ensemble: A case study of quartz

2006

Piezoelectric (strain) coefficients dij of quartz are calculated in terms of molecular dynamics as a function of pressure and temperature. We review the necessary formulas for the computation of electromechanical materials coefficients obtained at constant stress and temperature, and discuss how to overcome complications of the definition of polarization variations due to fluctuating box geometries. A method is employed suppressing significantly stochastic fluctuations of the estimators for piezoelectric coefficients. A recently suggested force field for the simulation of SiO2 reproduces available experimental data quite accurately. Predictions are made for the pressure dependence of dij of…

Tunable Bistability in a Three-Dimensional Spin-Crossover Sensory- and Memory-Functional Material

2005

Giant piezoelectricity in B/N doped 4,12,2-graphyne

2020

Abstract The effects of boron (B) and nitrogen (N) substitutions in 4,12,2-graphyne on its geometric structure and mechanical as well as electronic properties have been systematically investigated with the aid of density functional theory (DFT). The trend in the elastic properties of the substituted systems is determined by the doping positions and the type of the dopants. The Bader charge analysis reveals that the N dopant at the sp-site destroys the acetylenic linkage in 4,12,2-graphyne, but instead tends to form a polar bond, or even possibly a charge-shift bond. In particular, an obvious in-plane piezoelectricity is induced by foreign atom substitutions owing to the deformation of the p…

Elastic and piezoelectric properties of BaTiO3 at room temperature

1999

Abstract We have calculated the phonon dispersion curves of barium titanate (BaTiO 3 ) at room temperature. A lattice dynamical formalism using the shell model is used. This microscopic model includes the short-range interactions of axially symmetric type and the long-range Coulomb interactions and taking into account the electronic polarizability of constituent ions. Zone center phonon and a few phonons in the first Brillouin zone are used for fitting. The values of relevant parameters are critically analyzed. A calculation of the elastic and piezoelectric properties is presented and compared with the available experimental data.