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首页> 外文期刊>Journal of Materials Research >Dielectric relaxations, ultrasonic attenuation, and their structure dependence in Sr_4(La_xNd_(1-x))_2Ti_4Nb_6O_(30) tungsten bronze ceramics
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Dielectric relaxations, ultrasonic attenuation, and their structure dependence in Sr_4(La_xNd_(1-x))_2Ti_4Nb_6O_(30) tungsten bronze ceramics

机译：Sr_4（La_xNd_（1-x））_ 2Ti_4Nb_6O_（30）钨青铜陶瓷的介电弛豫，超声衰减及其结构依赖性

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摘要

The dielectric anomalies and their structure dependence were evaluated and discussed in Sr_4(La_xNd_(1-x))_2Ti_4Nb_6O_(30) ceramics, together with the analysis of ultrasonic velocity shift and attenuation spectra in the low-temperature range. The room-temperature structure was confirmed as the tetragonal in space group P4bm for all compositions. One diffuse ferroelectric peak and three relaxor ferroelectric peaks corresponding to the commensurate/incommensurate modulation of oxygen octahedra, polar clusters of A-site ion ordering, and B-site ion ordering, respectively, were observed in the composition with x = 0.25. With decreasing the radius difference between Al- and A2-ions (increasing x), the dielectric relaxations, especially the one originating from the polar clusters of A-site ion ordering, tended to increase significantly and overlap the diffuse ferroelectric peak, which was completely overlapped for x ≥ 0.75. This process just reflected the increased disordering degree of both A- and B-site ions, and the analysis of ultrasonic attenuation strongly supported the above conclusions on dielectric relaxations and their structural origins. The ultrasonic attenuation peak at approximately 100 K corresponded to the freezing process of the dielectric relaxations, and the fluctuation with composition of the ultrasonic attenuation peaks between 150 and 260 K suggested the possible structure variation.
机译：在Sr_4（La_xNd_（1-x））_ 2Ti_4Nb_6O_（30）陶瓷中评估并讨论了介电异常及其结构依赖性，并分析了低温范围内的超声速度位移和衰减谱。对于所有组合物，室温结构被确认为空间群P4bm中的四边形。在x ＝ 0.25的组成中，分别观察到一个与氧八面体的相称/不相称调制，A-位离子有序和B-位离子有序的极性簇相对应的扩散铁电峰和三个弛豫铁电峰。随着Al和A2离子之间的半径差减小（x增大），介电弛豫，特别是源自A位置离子有序极性簇的介电弛豫趋向于显着增加并与弥散铁电峰重叠，这完全是x≥0.75重叠。此过程仅反映了A和B位离子的无序度增加，并且超声衰减的分析有力地支持了上述有关介电弛豫及其结构起源的结论。大约100 K处的超声衰减峰对应于介电弛豫的冻结过程，并且在150到260 K之间随着超声衰减峰的组成而发生的波动表明可能存在结构变化。

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