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Design for Lead-free Ferroelectric Functional Materials using Layered Crystal Lattices

使用层状晶格的无铅铁电功能材料设计

基本信息

批准号：
14205096
负责人：
MIYAYAMA Masaru
金额：
$ 33.2万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-14205096/
关键词：
Bisumuth layer-structured ferroelectrics Lattice defects Oxygen vacancies Oxide ion conduction Domain structure Intergrowth structure Piezoelectric force microscopy ab initio calculation リーク電流圧電応答原子間力顕微鏡

项目摘要

Materials Design to realize novel ferroelectric and integrated functions was conducted using layered crystal lattices of Lead-free bismuth layer-structured oxides, and following results were obtained.1.Improvement of ferroelectric properties by defect engineeringA large permanent polarization of 28μC/cm^2 was confirmed in strontium bismuth tantalite single crystals with Sr deficiency and excess Bi. This was attributed to vacancies at the Sr sites leading to an increase in lattice distortion. Soft to hard polarization properties were realized by controlled doping of Rare-earth elements. Very large permanent polarizations were observed in bismuth titanate single crystals doped with higher-valent ions as W and Nb. This was attributed to decreases in oxygen vacancies and leakage current. The estimated vacancy-formation energies suggested that the doping results in a decrease of defect concentration and stabilization of the perovskite layers.2.Formation of intergrowth layered-structures and evaluationThe intergrowth superlattice of bismuth titanate and barium bismuth titanate showed a remanent polarization of 52μC/cm^2, which is the highest in Lead-free perovskite materials.3.Creation of integrated functionsThe Mn-substituted bismuth titanate single crystal showed semiconductivity along a-axis, and a memory-effect of the semiconductivity due to changes in polarized state was discovered. This effect was also confirmed in Lead-containing ferroelectrics, and thus expected for applications to new functional devices.

利用无铅铋层状氧化物的层状晶格进行了实现新型铁电和集成功能的材料设计，得到了以下结果：1.通过缺陷工程改善铁电性能在Sr不足、Bi过量的钽酸锶铋单晶中证实了28μC/cm ^2的大永久极化。这是由于在Sr位点的空位导致晶格畸变的增加。通过控制稀土元素的掺杂，实现了薄膜的软硬极化特性。在掺杂高价离子W和Nb的钛酸铋单晶中观察到非常大的永久极化。这归因于氧空位和漏电流的减少。估算的空位形成能表明，掺杂降低了缺陷浓度，稳定了钙钛矿层。2.共生层状结构的形成和评价钛酸铋和钛酸铋钡的共生超晶格显示出52μC/cm ^2的反射极化，这是无铅钙钛矿材料中最高的。3.集成功能的创建Mn取代的钛酸铋单晶显示出沿着a轴的磁导率，并且发现了由于极化状态的改变而引起的介电常数的记忆效应。这种效应在含铅铁电体中也得到了证实，因此有望应用于新的功能器件。