Free charge localization and effective dielectric permittivity in oxides  

作　　者：Mario Maglione 

机构地区：[1]ICMCB-CNRS,University of Bordeaux 87,Av Dr Schweitzer 33608 Pessac,France

出　　处：《Journal of Advanced Dielectrics》2016年第2期39-51,共13页先进电介质学报（英文）

摘　　要：This review will deal with several types of free charge localization in oxides and their consequences on the effective dielectric spectra of such materials.The first one is the polaronic localization at the unit cell scale on residual impurities in ferroelectric networks.The second one is the collective localization of free charge at macroscopic interfaces like surfaces,electrodes and grain boundaries in ceramics.Polarons have been observed in many oxide perovskites mostly when cations having several stable electronic configurations are present.In manganites,the density of such polarons is so high as to drive a net lattice of interacting polarons.On the other hand,in ferroelectric materials like BaTiO_(3)and LiNbO_(3),the density of polarons is usually very small but they can influence strongly the macroscopic conductivity.The contribution of such polarons to the dielectric spectra of ferroelectric materials is described.Even residual impurities as for example Iron can induce well-defined anomalies at very low temperatures.This is mostly resulting from the interaction between localized polarons and the highly polarizable ferroelectric network in which they are embedded.The case of such residual polarons in SrTiO_(3)will be described in more detail,emphasizing the quantum polaron state at liquid helium temperatures.Recently,several nonferroelectric oxides have been shown to display giant effective dielectric permittivity.It is first shown that the frequency/temperature behavior of such parameters is very similar in very different compounds(donor-doped BaTiO_(3),CaCu_(3)Ti_(4)O_(12),LuFe_(2)O_(4),Li-doped NiO,etc.).This similarity calls for a common origin of the giant dielectric permittivity in these compounds.A space charge localization at macroscopic interfaces can be the key for such extremely high dielectric permittivity.

关 键 词：Charged point defects ferroelectric oxides Perovskites space charges POLARONS 

分 类 号：O46[理学—电子物理学]