A combined theoretical and experimental study of the phase coexistence and morphotropic boundaries in ferroelectric-antiferroelectric-antiferrodistortive multiferroics

The physical nature of the ferroelectric (FE), ferrielectric (FEI) and antiferroelectric (AFE) phases, their coexistence and spatial distributions underpins the functionality of antiferrodistortive (AFD) multiferroics in the vicinity of morphotropic phase transitions. Using Landau-Ginzburg-Devonshire (LGD) phenomenology and a semi-microscopic four sublattice model (FSM), we explore the behavior of different AFE, FEI, and FE long-range orderings and their coexistence at the morphotropic phase boundaries in FE-AFE-AFD multiferroics. These theoretical predictions are compared with the experimental observations for dense Bi1-yRyFeO3 ceramics, where R is Sm or La atoms with the fraction 0 <= y <= 0.25, as confirmed by the X-ray diffraction (XRD) and Piezoresponse Force Microscopy (PFM). These complementary measurements were used to study the macroscopic and nanoscopic transformation of the crystal structure with doping. The comparison of the measured and calculated AFE/FE phase fractions demonstrate that the LGD-FSM approach well describes the experimental results obtained by XRD and PFM for Bi1-yRyFeO3. Hence, this combined theoretical and experimental approach provides further insight into the origin of the morphotropic boundaries and coexisting FE and AFE states in model rare-earth doped multiferroics. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

In this study, the physical nature and spatial distributions of FE, FEI, and AFE phases in multiferroic materials near morphotropic phase transitions were explored using LGD phenomenology and FSM models. Experimental observations on dense Bi1-yRyFeO3 ceramics were compared with theoretical predictions, showing that the LGD-FSM approach effectively describes the AFE/FE phase fractions. This combined theoretical and experimental approach provides insight into the origins of morphotropic boundaries and coexisting FE and AFE states in rare-earth doped multiferroics.