核壳结构对弛豫铁电体介电行为的影响

介电弥散和介电隔离率的温度非线性关系是弛豫铁电体的主要特征. 通过对掺杂成分以线性梯度递减的核壳结构进行热力学函数分析, 认为核壳结构能够在低温区保持较高的介电常数, 但不能导致介电隔离率与温度的非线性关系. 通过对不同浓度掺杂的铁电体扩散相变的比较, 认为掺杂浓度会影响晶粒掺杂成分的不均匀性, 在较宽的分布条件下会导致介电隔离率与温度的非线性关系. 因而在介电常数的峰值温度区域, 顺电相与铁电相的晶粒共存. 温度变化会影响两相比例及铁电畴的变化, 从而导致弛豫铁电体的介电弥散性. 核壳结构会增大介电弥散性. 铁电陶瓷的掺杂物种类、掺杂物浓度和烧结温度均会影响核壳结构的成分不均匀性和介电弥散性.

Influence of core-shell structure on dielectric behaviour in relaxor ferroelectrics

Dominant features of relaxor ferroelectrics are dielectric dispersion and the nonlinear relationship between reciprocal dielectric constant and temperature. The result of the analysis of the thermal dynamic function for core-shell structure in a grain shows that the core-shell structure doped with dopant in linear gradient descending ingredients can remain high dielectric constant at low temperatures, but cannot lead to the nonlinear relationship between reciprocal dielectric constant and temperature. By comparing diffusion transitions with different doping ingredients, it is suggested that the concentration of ingredient will affect the inhomogeneity of the doping ingredient. A wide distribution of the ingredient between grains by high doping concentration will result in the nonlinear relationship between reciprocal dielectric constant and temperature, and therefore the coexistence of grains in paraelectric phase and in ferroelectric phase in the peak area of dielectric constant. The change of measurement temperature will affect the ratio of the grains in two phases and the change in ferroelectric domains, which results in ferroelectric dielectric dispersion. The core-shell structure will increase the dielectric dispersion. Ferroelectric ceramics, doping species and their concentrations, and sintering temperature all can influence the inhomogeneity of core-shell structure and dielectric dispersion.