A Local Atomic Mechanism for Monoclinic-Tetragonal PhaseBoundary Creation in Li-Doped Na0.5K0.5NbO3Ferroelectric Solid Solution

Authors：Kong, Jing; Li, Lili; Liu, Jue; Marlton, Frederick P.; Jorgensen, Mads Ry Vogel; Pramanick, Abhijit^*

Source：Inorganic Chemistry, 2022, 61(10): 4335-4349.

DOI：10.1021/acs.inorgchem.1c03501

• POTASSIUM NIOBATE
• TRANSITIONS
• REFINEMENT
• LINBO3

ABO(3 )perovskites display a wide range of phase transitions, whichare driven by A/B-site centered polyhedral distortions and/or BO6octahedraltilting. Since heterogeneous substitutions at the A/B-site can locally alter bothpolyhedral distortions and/or tilting, they are often used to create phase boundaryregions in solid solutions of ABO3, where the functional properties are highlyenhanced. However, the relationships between doping-induced atomistic structuralchanges and the creation of phase boundaries are not always clear. One prominentexample of this is the Li-doped K0.5Na0.5NbO3(KNNL), which is considered apromising alternative to traditional Pb-based ferroelectrics. Although theelectromechanical properties of KNNL are enhanced for compositions near themorphotropic phase boundary (MPB), the atomistic mechanism for phasetransitions is not well understood. Here, we combined neutron total scatteringexperiments and density functional theory to investigate the long-range average andshort-range (similar to 10 A) structural changes in KNNL. We show that the averagemonoclinic-to-tetragonal (M-T) transition across the MPB in KNNL can be described as an order-disorder-type change, which isdriven by competition between a longer-range polarizationfield of monoclinic structural units and local distortions of the disorderedAO12polyhedra. The current study demonstrates a way to clarify dopant-induced local distortions near phase boundaries in complexsolid solution systems, which will be important for the rational design of new environmentally sustainable ferroelectrics.

• Institution
  中国科学院