Abstract
ABO3 perovskites display a wide range of phase transitions, which are driven by A/B-site centered polyhedral distortions and/or BO6 octahedral tilting. Since heterogeneous substitutions at the A/B-site can locally alter both polyhedral distortions and/or tilting, they are often used to create phase boundary regions in solid solutions of ABO3, where the functional properties are highly enhanced. However, the relationships between doping-induced atomistic structural changes and the creation of phase boundaries are not always clear. One prominent example of this is the Li-doped K0.5Na0.5NbO3 (KNNL), which is considered a promising alternative to traditional Pb-based ferroelectrics. Although the electromechanical properties of KNNL are enhanced for compositions near the morphotropic phase boundary (MPB), the atomistic mechanism for phase transitions is not well understood. Here, we combined neutron total scattering experiments and density functional theory to investigate the long-range average and short-range (∼10 Å) structural changes in KNNL. We show that the average monoclinic-to-tetragonal (M-T) transition across the MPB in KNNL can be described as an order-disorder-type change, which is driven by competition between a longer-range polarization field of monoclinic structural units and local distortions of the disordered AO12 polyhedra. The current study demonstrates a way to clarify dopant-induced local distortions near phase boundaries in complex solid solution systems, which will be important for the rational design of new environmentally sustainable ferroelectrics.
Original language | English |
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Pages (from-to) | 4335-4349 |
Number of pages | 15 |
Journal | Inorganic Chemistry |
Volume | 61 |
Issue number | 10 |
DOIs | |
State | Published - Mar 14 2022 |
Funding
Funding support from CityU (projects nos. 7005121 and 6000688) is gratefully acknowledged. The work described in this paper was fully/partially supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (project no. eg CityU 11306720). F.M. and M.R.V.J. gratefully acknowledge the support of the Danish Agency for Science, Technology and Innovation (DANSCATT). Affiliation with the Center for Integrated Materials Research (iMAT) at Aarhus University is gratefully acknowledged. J.K. and F.P.M. gratefully acknowledge Michelle Everett for assisting with measurements at the NOMAD instrument. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. This work was carried out using computational facilities, CityU Burgundy, managed and provided by the Computing Services Centre at the City University of Hong Kong.