Silver solid solution piezoelectrics

Using density functional theory calculations, we investigate the feasibility of using silver on the perovskite A-site in high-performance lead-free piezoelectrics. The calculations show that silver atoms are ferroelectrically active and can off-center by 0.5 Angstrom. To induce Ag ferroelctric behavior absent in pure AgNbO3 we explore solid solutions of AgNbO3 with well-known simple perovskites PbTiO3, BaZrO3, and BaTiO3. For the AgNbO3-PbTiO3 solid solution, we predict a morphotropic phase boundary near (AgNbO3)(3/8)(PbTiO3)(5/8). We find an unusual sequence of compositional phase transitions in AgNbO3-BaZrO3 and AgNbO3-BaTiO3 which are due to the effects of volume expansion in perovskites. For the AgNbO3-BaTiO3 solid solution we find two morphotropic phase boundaries at 12.5% and 37.5% AgNbO3 compositions with favorable piezoeletric properties and indications of high T-C. (C) 2004 American Institute of Physics.