Preparation and dielectric properties of Ba4RFe0.5Nb9.5O30 (R = La, Nd, Eu, Gd) unfilled tungsten bronze ceramics
Preparation and dielectric properties of Ba4RFe0.5Nb9.5O30 (R = La, Nd, Eu, Gd) unfilled tungsten bronze ceramics
复制标题
Ba4RFe0.5Nb9.5O30（R=La、Nd、Eu、Gd）无填充钨青铜陶瓷的制备及介电性能
DOI：
10.1016/j.jallcom.2018.09.241
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发表时间：
2019-01-30
影响因子：
6.2
通讯作者：
Fang, Liang
中科院分区：
文献类型：
--
作者：
Guo, Zhe;Wu, Shan;Fang, Liang
采用标准固相烧结法制备了一般结构式为Ba4RFe0.6Nb9.5O30 (R= La, Nd, Eu, Gd) （BRFN）的无铅弛豫铁电体，并基于其结构系统地讨论了a位离子占据对其电学性能和介电特性的影响。所有化合物均呈P4bm空间群的四方钨青铜（TTB）结构，其中Al位被R3+离子独占，A2位被Ba2+离子独占，而Fe3+和Nb5+离子随机分布在B1和B2位之间。此外，频率和温度使BRFN5呈现出宽的介电常数峰，并伴有宽的频散。随着a1位离子尺寸的减小，最大介电常数温度逐渐升高，频率色散逐渐减小。复阻抗谱分析表明，BRFN陶瓷的高温导电行为仅受晶界的影响，并且随着a1位离子尺寸的减小，活化能增加。所有化合物的直流电导率都来源于氧空位二次电离产生的电子，可能是氧空位离子与电子的杂化传导机制所致。BRFN陶瓷的拉曼光谱大多包含与八面体NbO6内部振动相关的多组分和宽频带，并且随着a1位离子尺寸的减小，Nb-O的拉伸发生变化。(C) 2018 Elsevier B.V.版权所有
Lead-free relaxor ferroelectrics with the general structural formula Ba4RFe0.6Nb9.5O30 (R= La, Nd, Eu, Gd) (BRFN) were prepared using a standard solid-state sintering route, and the influence of the A site ion occupation on their electrical properties and dielectric characteristics was systematically discussed based on their structure. All compounds presented tetragonal tungsten bronze (TTB) structure with space group P4bm, where the Al sites were exclusively occupied by R3+ ions and the A2 sites were exclusively occupied by Ba2+ ions, while the Fe3+ and Nb5+ ions were randomly distributed between the B1 and B2 sites. Furthermore, frequency and temperature caused BRFN5 to present a broad permittivity peak accompanied by wide frequency dispersion. The maximum dielectric constant temperature gradually increased and the frequency dispersion gradually decreased as the A1-site ion size decreased. Complex impedance spectroscopy indicated that only the grain boundaries contributed to the conductive behavior of BRFN ceramics at high temperature, and the activation energy increased as the A1-site ion size decreased. The direct current (DC) conductivity of all compounds originated from the electrons generated by the second ionization of the oxygen vacancies and might have been caused by the hybrid conduction mechanism of the oxygen-vacancy ions and electrons. Raman spectra of the BRFN ceramics mostly contained multi-component and broad bands related to the internal vibrations of the octahedral NbO6 , and as the size of the A1-site ion decreased, the Nb-O stretching changed. (C) 2018 Elsevier B.V. All rights reserved.