Electric-Field-Induced Phase Transition in Mn-Doped (K0.48Na0.48Li0.04)NbO3 Lead-Free Ceramics

Abstract

In situ applied-electric-field high-resolution X-ray diffraction has been used to study the field-induced response of Mn-doped (K 0.48 Na 0.48 Li 0.04 )NbO 3 (KNN-L) ceramics produced using the conventional mixed-oxide processing route. Ferroelectric domains are observed with transmission electron microscopy with indications of nano-segrega-tion of Mn. Rietveld refinement (FULLPROF Suite) is used to refine the diffraction patterns, and a phase change from orthorhombic symmetry with space group A mm 2 to tetragonal symmetry with space group P4 mm is observed when the applied field exceeds 1.4 kV/mm. Phase coexistence between the two phases is also observed at applied fields between 1.2 kV/mm and 1.3 kV/mm with possible implications of being the coercive field E C value of the sample. A better understanding of the structural behaviour of this type of lead-free ceramics will lead to improvements in their piezoelectric and electromechanical properties.