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Detection of Negative Thermal Expansion in a Single Crystal of Sr 0.75 Ba 0.25 Nb 6 O 2 Relaxor Ferroelectric by X-Ray Diffraction Analysis
Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques Pub Date : 2020-07-07 , DOI: 10.1134/s1027451020030234
A. P. Dudka

Abstract

The atomic structure of a single crystal of Sr0.75Ba0.25Nb6O2 representing a relaxor ferroelectric is determined from X-ray diffraction data. At nine temperatures within a range of 93–480 K, 12 experiments are performed. The experimental facilities (area detector, goniometer, and sample cooling system) are calibrated. The region of negative thermal expansion with respect to the unit-cell parameter с is revealed at 272–324 K. In the same region, an electrical resistance anomaly is observed. It is found that the structural parameters have a singularity at 296 K, in particular, an unusual thermal motion of atoms is observed. This correlates with a kink in the resistance–temperature curve at 297.5 K. The obtained results and analysis of published data indicate that, near room temperature, several physical properties of Sr0.75Ba0.25Nb6O2 relaxor at once have singularities, which can be explained by the revealed lattice instability.


中文翻译:

X射线衍射分析检测Sr 0.75 Ba 0.25 Nb 6 O 2弛豫铁电单晶中的负热膨胀

摘要

由X射线衍射数据确定代表弛豫铁电体的Sr 0.75 Ba 0.25 Nb 6 O 2的单晶的原子结构。在93-480 K范围内的9个温度下,进行了12个实验。实验设备(区域检测器,测角仪和样品冷却系统)已经过校准。相对于晶胞参数с的负热膨胀区域在272–324 K处发现。在同一区域,观察到电阻异常。发现结构参数在296 K处具有奇异性,特别是观察到原子的异常热运动。这与297.5 K时电阻-温度曲线的扭结有关。所得结果和已发表数据的分析表明,在室温附近,Sr 0.75 Ba 0.25 Nb 6 O 2弛豫器的几个物理性质立即具有奇异性,这可以由揭示的晶格不稳定性来解释。
更新日期:2020-07-07
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