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Defect structure and dielectric properties of Bi-based pyrochlores probed by positron annihilation

机译：正电子ni没法检测Bi基烧绿石的缺陷结构和介电性能

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摘要

Positron annihilation lifetime (PAL) and Doppler broadening (DB) techniques have been performed to identify structural defects of the bismuth based pyrochlore systems with generic formula (Bi1.5Zn0.5)(Zn0.5-x/3TixNb1.5-2x/3)O-7 (x = 0, 0.25, 0.5, 1.0, 1.5). We found that all studied compounds contain substantial amount of the lattice vacancy defects, the variation of the annihilation lifetime suggests that the defects structure undergoes significant changes. The complex defects could be produced with increasing content of Ti, resulting in a drop in the intensity I-2 in the Ti-rich sample. At 1 MHz their dielectric constant (epsilon') varies from 150 for Ti-poor system to 210 for Ti-rich system and loss tangent (tan delta) remains rather low level. The high dielectric constant response of the BZTN ceramics is attributed to loosening state of cations located in the center of octahedral, so favor off-center displacement. The occurrence of complex defects help to enhance the dielectric constant. (c) 2006 Elsevier B.V. All rights reserved.
机译：已经进行了正电子an灭寿命（PAL）和多普勒展宽（DB）技术来鉴定具有通式（Bi1.5Zn0.5）（Zn0.5-x / 3TixNb1.5-2x / 3）的铋基烧绿石体系的结构缺陷O-7（x = 0，0.25，0.5，1.0，1.5）。我们发现所有研究的化合物都包含大量的晶格空位缺陷，the没寿命的变化表明缺陷结构发生了显着变化。随着Ti含量的增加，可能会产生复杂的缺陷，从而导致富Ti样品中强度I-2下降。在1 MHz时，其介电常数（ε）从贫钛系统的150变为富钛系统的210，损耗角正切（tanδ）仍然很低。 BZTN陶瓷的高介电常数响应归因于位于八面体中心的阳离子的松散状态，因此有利于偏心位移。复杂缺陷的出现有助于提高介电常数。 （c）2006 Elsevier B.V.保留所有权利。

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