New considerations on the role of covalency in ferroelectric niobates and tantalates

被引：30

作者：

Villesuzanne, A ^{[1
]}

Elissalde, C ^{[1
]}

Pouchard, M ^{[1
]}

Ravez, J ^{[1
]}

机构：

[1] Inst Chim Mat Condensee Bordeaux, CNRS, F-33608 Pessac, France

来源：

EUROPEAN PHYSICAL JOURNAL B | 1998年 / 6卷 / 03期

关键词：

D O I：

10.1007/s100510050553

中图分类号：

O469 [凝聚态物理学];

学科分类号：

070205 ;

摘要：

Values of Curie temperature, T-C, and microwave relaxation frequency, f(r), of ferroelectric niobates and tantalates are found to be closely related to the metal-oxygen network covalency. Correlations previously evidenced in perovskite-type relaxors (PSN, PST) are confirmed here for K(Ta1-xNbx)O-3 (KTN) compositions. The investigated physical characteristics, T-C and f(r), are determined via dielectric measurements performed in a wide frequency range (10(2)-10(9) Hz) and as a function of temperature (250-800 K). On a theoretical point of view, bond covalencies are evaluated through tight-binding band structure calculations. The complex role of covalency on the metal potential is precised. Two antagonist effects acting on both the short-range interatomic repulsions and time rigidity and stability of the oxygen-metal network are discussed. The validity of this approach is comforted through the example of the oxyfluoride K3Li1.5Ta5O14.5F0.5.

引用

页码：307 / 312

页数：6

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