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arXiv · 1906.01384

Mapping the structural transitions controlled by the trilinear coupling in Ca3-xSrxTi2O7

Marie Kratochvilova·Fei-Ting Huang·Maria-Teresa Fernandez Diaz·Milan Klicpera·Sarah J. Day·Stephen P. Thompson·Yoon-Seok Oh·Bin Gao·Sang-Wook Cheong·Je-Geun Park
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Abstract

We present the results of the high-temperature neutron and x-ray diffraction experiments on the Ca3-xSrxTi2O7 (x = 0.5, 0.8, 0.85, 0.9) compounds. The ferro- to paraelectric transition in these hybrid improper ferroelectric materials arises from the so-called trilinear coupling. Depending on the Strontium content, various structures and phase transitions, different from theoretical predictions, emerge. The in-situ x-ray powder diffraction indicates a direct ferro- to paraelectric transition between the orthorhombic A21am and tetragonal undistorted I4/mmm phase for x < 0.6. We identified a reduction in the trilinear coupling robustness by increasing the Sr-doping level to lead to the emergence of the intermediate tetragonal P42/mnm phase and the gradual suppression of the orthorhombic phase. The observed character of the structure transitions and the Ca3-xSrxTi2O7 phase diagram are discussed in the framework of theoretical models of other related hybrid improper ferroelectric systems.

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Marie Kratochvilova, Fei-Ting Huang, Maria-Teresa Fernandez Diaz, Milan Klicpera, Sarah J. Day, Stephen P. Thompson, Yoon-Seok Oh, Bin Gao, Sang-Wook Cheong, Je-Geun Park. 2019-06-04. Mapping the structural transitions controlled by the trilinear coupling in Ca3-xSrxTi2O7. https://doi.org/10.1063/1.5089723

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