Tweed domains in ferroelectrics with compositions at the morphotropic phase boundary

Observations by transmission electron microscopy reveal the general existence of tweed domains on nanoscopic and mesoscopic scales in unpoled 0.7Pb(Mg1/3Nb2/3)O3–0.3PbTiO3, 0.92Pb(Fe1/2Nb1/2)O3–0.08PbTiO3 and Pb(Fe1/2Nb1/2)O3 single crystals. These crystals consist of many tweed regions. Each of these includes only single twinning variant tweeds along either <110> or <100>. Mesoscopic needle domains or wedge boundaries were created when two tweed regions meet. The tweed structure could limit possible polar domain states that determine macropolarization states of materials.