Structural phase transitions and electrical properties of (KxNa1−x)NbO3-based ceramics modified with Mn

Abstract (K 0.5 Na 0.5 )NbO 3 (KNN) ceramics and KNN containing Li, Ta modified with 2 mol% of manganese have been produced using the mixed-oxide ceramics synthesis route. The structure and properties of these piezoelectric ceramics modified with manganese have been investigated using high resolution X-ray diffraction and electrical characterisation. The structural information about the ceramics was determined by Rietveld refinement with Fullprof. The phase transition temperatures observed with X-ray diffraction compares well with the values from dielectric studies. The addition of Mn slightly reduced the phase transition temperatures and for the sample containing only Li, the phase changed from orthorhombic to monoclinic phase with space group Pm . The dielectric, piezoelectric and ferroelectric properties of the samples decreased with Mn addition due to hard doping effects resulting from oxygen vacancies in the perovskite lattice.