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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(LaxNd1-x)(2)Ti4Nb6O30 tungsten bronze ceramics
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Dielectric relaxations, ultrasonic attenuation, and their structure dependence in Sr-4(LaxNd1-x)(2)Ti4Nb6O30 tungsten bronze ceramics

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摘要

The dielectric anomalies and their structure dependence were evaluated and discussed in Sr-4(LaxNd1-x)(2)Ti4Nb6O30 ceramics, together with tile 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 tile radius difference between A1- and A2-ions (increasing x), the dielectric relaxations, especially the one originating from 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 oil 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.

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