Electric field-induced polarization rotation and ultrahigh piezoelectricity in PbTiO3

Polarization rotation, phase changes, and piezoelectric property of PbTiO3 under high electric field have been investigated using a Landau-Ginzburg-Devonshire phenomenological approach. Electric field versus temperature phase diagram has been constructed. Tetragonal (T)-monoclinic (MA)-rhombohedral (R) phase transition occurs when electric field is applied along pseudo-cubic [111] axis, and piezoelectric coefficient d33 is remarkably enhanced near the critical electric field for MA-R transition. With electric field applied along pseudo-cubic [011] axis, the polarization rotation involves the other two monoclinic phases (MB and MC), and ultrahigh d33 over 8000 pC/N has been found at the monoclinic-orthorhombic (M-O) transition region. The critical field for M-O transition (∼1000 MV/m) can be greatly lowered under hydrostatic pressure. Based on the reported strain gradient induced polarization rotation in epitaxial film, flexoelectric coefficient μ12 of PbTiO3 is estimated to be ∼156–312 nC/m at room temperature.