Silver solid solution piezoelectrics

Abstract

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 $0.5\mathrm{\AA }$ . To induce $\mathrm{Ag}$ ferroelctric behavior absent in pure ${\mathrm{AgNbO}}_3$ we explore solid solutions of ${\mathrm{AgNbO}}_3$ with well-known simple perovskites ${\mathrm{PbTiO}}_3$ , ${\mathrm{BaZrO}}_3$ , and ${\mathrm{BaTiO}}_3$ . For the ${\mathrm{AgNbO}}_3–{\mathrm{PbTiO}}_3$ solid solution, we predict a morphotropic phase boundary near ${\left({\mathrm{AgNbO}}_3\right)}_{3∕8}{\left({\mathrm{PbTiO}}_3\right)}_{5∕8}$ . We find an unusual sequence of compositional phase transitions in ${\mathrm{AgNbO}}_3–{\mathrm{BaZrO}}_3$ and ${\mathrm{AgNbO}}_3–{\mathrm{BaTiO}}_3$ which are due to the effects of volume expansion in perovskites. For the ${\mathrm{AgNbO}}_3–{\mathrm{BaTiO}}_3$ solid solution we find two morphotropic phase boundaries at 12.5% and 37.5% ${\mathrm{AgNbO}}_3$ compositions with favorable piezoeletric properties and indications of high $T_C$ .