Phase diagram of unpoled lead-free – ceramics

A phase diagram for unpoled ceramics in the lead-free ( 1 − x ) ( Bi 1 / 2 Na 1 / 2 ) TiO 3 – x BaTiO 3 binary system is constructed for the first time based on transmission electron microscopy (TEM) and dielectric study. In contrast to the reported phase diagram determined using poled ceramics, an additional phase region exhibiting P4bm nanodomains was revealed. A new concept “relaxor antiferroelectric” was proposed to describe the unique short-range antiferroelectric order of this phase. The results suggest that electric field-induced phase transitions must be taken into consideration in optimizing the piezoelectric properties in these lead-free ceramics.