Tailoring Strain Properties of (0.94-x)Bi_(1/2)Na_(1/2)TiO_3-0.06BaTiO_3-xK_(0.5)Na_(0.5)NbO_3 Ferroelectric/Relaxor Composites

摘要

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 nonerg-odic relaxor (seed). In this study, we investigate the effect of K_(0.5)Na_(0.5)NbO_3 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)Bi_(1/2Na_(1/2)TiO_3-0.06Ba TiO_3-xK_(0.5)Na_(0.5)NbO_3 as a matrix. The strain of all matrices, independent of their K_(0.5)Na_(0.5)NbO_3 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 K_(0.5)Na_(0.5)NbO_3 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.