Papers by Keyword: Ferroelectric

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Authors: Li Li
Abstract: Pt/Bi3.15Nd0.85Ti3O12(BNT)/Pt ferroelectric capacitors were monitored using in situ X-ray irradiation with 10 keV at BL14B1 beamline (Shanghai Synchrotron Radiation Facility). BL14B1 combined with a ferroelectric analyzer enabled measurements in situ of electrical performance. The hysteresis curve (PE) of distortion depended on the polarization during irradiation, but the diffracted intensities of the (117) peak did not change in the beginning. The PE curve had a negligible change from 2.09×109 Gy to 4.45×109 Gy. Finally, both Pr and Pr+ very rapidly increased, but the intensities of (117) decreased. The hysteresis loops were remarkably deformed at the maximum total dose of 4.87×109 Gy.
Authors: Zheng Li, Y.G. Xiao, M.H. Tang, J.W. Chen, H. Ding, S.A. Yan, Y.C. Zhou
Abstract: A theoretical model for radiation effect in a metal-ferroelectric-semiconductor (MFS) field-effect transistor was proposed by considering the fixed charges (Qfx) and interface charges (Qit) induced by ionizing radiation. In this model, the energy band-bending and surface charge in Si at a given gate bias were calculated systematically as a function of fixed charges (Qfx) and interface charges (Qit). The drain-source current (ID) was derived in an exact form without any approximation. All modeling done in this work was generalized to both n and p type Si substrates with an easy sign of the Fermi level potential in the formalism. The derived results demonstrate that the symmetry of polarization versus gate voltage curve of the MFS structure degrades when Qfx and Qit increase, which can explain the imprint behavior successfully. Additionally, the residual polarization in the ferroelectric field-effect transistor decreases with increasing Qfx and Qit, which can account for the polarization reduction. As expected, the calculated transfer characteristic of the ferroelectric FET shows that the subthreshold voltage is significantly affected by Qfx and Qit. This investigation may provide some useful insights for the space applications of ferroelectric FET’s.
Authors: Xiao Qing Chen, Dai Ning Fang
Authors: K.P. Jayachandran, J.M. Guedes, H.C. Rodrigues
Abstract: A stochastic optimization procedure incorporating a continuum modelling is used to identify the optimal texture (orientation distribution) parameters of ferroelectrics (FEs) for piezoelectric applications. FE polycrystals differ significantly from single crystals because of the presence of variously oriented crystallites. The orientation of FE crystals plays a critical role in the anisotropy of their piezoelectric properties. The set of combination of variables, known as solution space, which dictates the texture of crystallites is unlimited. Crystallographic orientation in FEs is characterised through Euler angles . The macroscopic properties of a ceramic FE, differ significantly from those of single crystals mainly due to the imperfect alignment of the crystallographic axes of the constituent domains or crystallites. This suggests that piezoelectric properties can be tailored by a proper choice of the parameters which control the orientation distribution. Nevertheless, this choice is complicated and it is impossible to analyze all possible combinations of the distribution parameters or the angles themselves. Stochastic optimization combined with a generalized Monte Carlo scheme optimizes the objective functions, the effective piezoelectric coefficients . Objective functions are calculated using the homogenization method at each orientation configuration chosen by the optimization algorithm. A modified simulated annealing is employed to describe the stochastic optimization. Here we have simulated the texture of polycrystals using a simple model with a Gaussian distribution. Optimal design variables that enhance the macroscopic piezoelectricity are identified.
Authors: Sukrit Sucharitakul, Rattikorn Yimnirun, Yongyut Laosiritaworn
Abstract: A 2D Monte Carlo simulation was done as an approach to get further insight of acceptor-doped ferroelectric material. By utilizing vector model allowing 14 directions of orientation for ferroelectric systems, Metropolis algorithm was applied on DIFFOUR Hamiltonian to obtain hysteresis profiles. Subjected to different concentration of acceptor dopants, power law scaling of hysteresis properties were obtained as functions of external parameters such as temperature, external field amplitude and frequency. The hysteresis loop shape and properties agreed well with those obtained experimentally.
Authors: Yong Fei Cui, Joe Briscoe, Steve Dunn
Abstract: We use BaTiO3 as a model photocatalyst to investigate the effect of ferroelectricity on catalytic activity against photocatalytic decolourisation of Acid Black 1. We find that there is a strong relationship between the degree of ferroelectric nature of the BaTiO3 and the catalytic activity. When Ag is photodeposited onto BaTiO3 to produce a modified BaTiO3, the higher tetragonal material content shows the highest photocatalytic efficiency even though there is a reduced surface area due to heat treatment. This change in the performance of the catalyst is associated with improvements in charge carrier separation due to the internal space charge layer formed in a ferroelectric due to the internal dipole.
Authors: Paweł Wawrzała, Dariusz Bochenek
Abstract: This paper presents a new way of using the classical Preisach distribution to the analytical description of the behavior of ceramic ferroelectrics in a wide range of temperatures. The iteration method have been used to investigate the Preisach distribution from polarization-electric field hysteresis loops to observe the composition and temperature variation of the some parameters in lead barium zirconate titanate stannate ceramic samples. Received Preisach distributions from P-E hysteresis loops were modeled by selected analytical functions to find useful parameters to observing the evolution of the hysteresis loops with temperature. This type of analysis can allow a more complete understanding of the relaxor properties occurring in these kind of materials, and may be used to examination the changes of temperature changes of piezoelectric sensors.
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