Predicting Dielectric Properties of Doped BaTiO3 Using First-Principles and Monte Carlo Simulations

We investigate the dielectric properties of homovalent (M4+)-doped Ba(Ti1−xMx)O3 compositions using a two-dimensional Ising-like network. The model is mainly based on the interaction of permanent and induced dipoles and allows us to simulate the collective behavior of atoms at finite temperatures. In contrast to previous publications, we also include first-principles calculations to model the local environment and interaction of the B-site atoms. Furthermore, in order to describe the corresponding physics more accurately, we introduce an additional degree of freedom for the polarization direction. Our simulations provide an insight into the formation of polar clusters, the evolution of spontaneous polarization at different concentrations of dopants, and the response to external fields. For the purpose of studying the dielectric properties, the model is used to calculate hysteresis curves and related quantities.

Исследование механизмов изменения степени униполярности при термической обработке сильно легированных кристаллов LiNbO-=SUB=-3-=/SUB=-:ZnO

Phenomenological mechanisms of an increase in unipolarity degree at thermal treatment under short circuit conditions of strongly doped crystals are researched by comparison with thermal behavior of nominally pure LiNbO3 crystals of congruent composition. It has been shown that an increase in unipolarity degree, and correspondingly vanishing of domain structure in strongly doped LiNbO3:ZnО crystals starts by thermal decomposition of charged polar clusters. These clusters stabilize domain walls. The decomposition is accompanied by sharp jump-like injection of additional charge carriers (Li+ cations). Due to this, conductivity of LiNbO3:ZnО crystals is one order of magnitude higher at temperature above 800K than in nominally pure LiNbO3 crystals of congruent composition. The injection leads to decomposition of domain structure in LiNbO3:ZnО crystals in spite of LiNbO3 crystals of congruent composition.

A highly proton-/vanadium-selective perfluorosulfonic acid membrane for vanadium redox flow batteries

The polar clusters of Nafion are blocked by the incorporation of the nanohybrid, which contributes to suppress vanadium ions crossover.