Spontaneous ferroelectric order in lead-free relaxor Na1/2Bi1/2TiO3-based composites

Short-range ordered polar nanoregions are key to the giant electromechanical properties exhibited by relaxorferroelectrics. Stabilization of the long-range ferroelectric order in relaxor systems has typically been achievedby applying external fields. In this work, spontaneous (zero-field) ferroelectric order is demonstrated inthe composites constituting of nonergodic relaxor matrix phase 0.91Na1/2Bi1/2TiO3-0.09BaTiO3with ZnOinclusions. Direct structural evidence is provided for the long-range ferroelectric order in the composites usingin situelectric-field-dependent synchrotron investigations and23Na nuclear magnetic resonance spectroscopy.Thermodynamic analysis incorporating microelasticity reveals the role of spatial residual stress in stabilizingthe ferroelectric order. The work provides a direct correlation between the stabilized ferroelectric order andenhanced thermal stability, which can be utilized to guide the design of spontaneous long-range order in otherrelaxor systems.