The electric field induced phase transition behavior of lead lanthanum zirconate titanate stannate (PLZTS) ceramics was investigated. PLZTS undergoes a tetragonal antiferroelectric(AFETet)to rhombohedral ferroelectric(FERh)phase transition with the application of an electric field. The volume increase associated with this antiferroelectric (AFE)–ferroelectric (FE) phase transition plays an important role with respect to actuator applications. This volume increase involves an increase in both transverse and longitudinal strains. TheEfield at which the transverse strain increases is accompanied by an abrupt jump in polarization. The longitudinal strain, however, lags behind this polarization jump exhibiting a slight decrease at the onset of phase switching. This decoupling was related to the preferentially oriented AFE domain configuration, with its tetragonalc-axis perpendicular to the applied electric field. It is suggested that phase switching involves multiple steps involving both structural transformation and domain reorientation. ©1997 American Institute of Physics.