四方晶系
铁电性
材料科学
反铁电性
凝聚态物理
钨
极地的
调制(音乐)
散射
中子散射
超晶格
晶体结构
结晶学
光学
电介质
物理
化学
光电子学
声学
冶金
天文
作者
Victor Krayzman,Alexeï Bosak,Helen Y. Playford,Bruce Ravel,Igor Levin
标识
DOI:10.1021/acs.chemmater.2c02367
摘要
The nanoscale structure of Sr0.61Ba0.39Nb2O6, a classic uniaxial relaxor ferroelectric crystallizing with the tetragonal tungsten bronze (TTB) structure and exhibiting an incommensurate modulation, has been determined by atomistic refinements using combined data from variable-temperature neutron total scattering, extended X-ray absorption fine structure, and three-dimensional single-crystal diffuse scattering. We found the modulation to arise from the intergrowth of structural slabs featuring distinct types of octahedral rotations directed to minimize octahedral deformations. This modulation involves displacements of the A cations (Sr and Ba) but exerts no significant effect on the polar displacements of Nb. Our results demonstrated the coexistence of competing polar Γ3– and antipolar Γ2– modes for off-centering of Nb above the nominal ferroelectric transition temperature of 350 K. The nanoscale-correlated antipolar distortions, which exhibit their largest amplitudes at 425 K, are suppressed below the transition. We identified coupling between the polar off-centering of Nb on its two symmetrically distinct sites as a fundamental characteristic controlling the ferroelectric-to-relaxor crossover in TTBs. We then used it to propose a simple microscopic interpretation for the previously established empirical trend that links crystal–chemical parameters in these systems to their polar response.
科研通智能强力驱动
Strongly Powered by AbleSci AI