Tailoring Strain Properties of (0.94-x)Bi1/2Na1/2TiO3-0.06BaTiO3-xK0.5Na0.5NbO3 Ferroelectric/Relaxor Composites

A remarkable progress in the quest of lead-free piezoceramics for actuator applications has been made with the development of incipient piezoceramics featured by giant strains. A drawback, however, is the high electric field required to generate this giant strain. A powerful approach to overcoming this drawback lies in relaxor/ferroelectric (FE) composites comprised such giant strain materials (matrix) and a FE or nonergodic relaxor (seed). In this study, we investigate the effect of K0.5Na0.5NbO3 content in the matrix and the volume ratio of seed to matrix using composites of 0.93Bi(1/2)Na(1/2)TiO(3)-0.07BaTiO(3) as a seed and (0.94-x)Bi1/2Na1/2TiO3-0.06BaTiO(3)-xK(0.5)Na(0.5)NbO(3) as a matrix. The strain of all matrices, independent of their K0.5Na0.5NbO3 content, was found to be enhanced by adding a certain amount of seed. An optimum strain is achieved for the composite comprised of a matrix with x=0.02 K0.5Na0.5NbO3 and 10% seed. By means of a differential analysis on the temperature-dependent dielectric permittivity, it was shown that the seed phase is still present in the composites despite the naturally expected diffusion process during sintering.