The effect of external field symmetry on the antiferroelectric-ferroelectric phase transformation

The antiferroelectric (AFE)-ferroelectric (FE) phase transformation under de bias and hydrostatic pressure conditions in tin-modified lead zirconate titanate ceramics [Pb(Zr,Sn,Ti)O-3, i.e., PZST] was investigated. The shifting of transformation temperature under these conditions and an electric field induced lattice softening are reported. Depending on the symmetry of external applied fields, the thermal stability region of one phase can be expanded at the expense of another. Experimental results indicate that a symmetric external field (such as hydrostatic pressure) tends to stabilize the AFE phase region, whereas an asymmetric external field (such as electric field) tends to extend the FE phase region. These observations are found to be generally consistent with many ferroelectric and antiferroelectric materials exhibiting a displacive structural phase transformation. Results are compared with the Clausius-Clapeyron relationship, and fundamental issues underlying the thermodynamic relationship and field-induced lattice softening behavior are discussed from the perspective of lattice dynamics theory. (C) 1996 American Institute of Physics.