Plastic deformation studies of lead-free KNbO3 ferroelectric perovskites
Many electromechanical devices use ferroelectric perovskites, often PbTiO3 or Pb(Zr,Ti)O3. Efforts to reduce the use of lead in these devices require a replacement material and KNbO3 (KNO) is a suitable candidate. KNO is a ferroelectric perovskite with appropriate electronic and optical properties, and good chemical stability. Its structure varies with temperature more than some perovskites; it is cubic and not ferroelectric above 435°C, tetragonal between 435°C and 225°C and orthorhombic at room temperature. The aim of this study is to investigate the structure and behaviour of dislocations and domain walls in KNO after plastic deformation. The guiding question for the research is: do perovskite materials have similar characteristic dislocation behaviours or does chemical composition have a significant effect? This investigation involves both physical testing and microscopy, and atomistic simulations and electronic structure calculations.