Coherent off-centering of the A-site cation is frustrated on the rigid pyrochlore lattice, preventing the ferroelectric-paraelectric phase transition in majority of pyrochlore oxide materials.1 Of the few ferroelectric pyrochlores is the series Cd2Nb2O7-xSx. While these materials have been studied for some time,2-5 their low temperature structure is still not well understood, hindering the understanding of ferroelectric phase transitions and long-range ordering of distortions in pyrochlores. In this work we will use synchrotron X-ray scattering data to characterize the low-temperature ferroelectric structures of Cd2Nb2O7-xSx (x= 0, 0.25, 0.5, 0.7) and better understand the structural changes accompanying the ferroelectric to paraelectric phase transition. Based on this understanding, new polar pyrochlores will be studied using two approaches. The first approach is to relieve the frustration of the A-site lone pairs through partial substitution of bigger/smaller cations into the A-site. Second, introducing bigger cations into the B-site will be evaluated to understand the interplay between the BO6 and A2O’ pyrochlore sublattices, which are known to influence each other.6 The ultimate goal of this study is to understand the origins of long-range order in pyrochlores to rationally design new polar pyrochlores for electronic applications.

Understanding distortions in the cubic pyrochlore lattice towards the design of polar materials

255th National Meeting (2018)

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