CRYSTAL SYMMETRY, OPTICAL PROPERTIES, AND FERROELECTRIC POLARIZATION OF Bi4Ti3O12 SINGLE CRYSTALS

Abstract

Optical and electrical measurements on thin sections of Bi₄Ti₃O₁₂ in orientations not previously measured have yielded the following results. The symmetry is monoclinic, point group m. The spontaneous polarization P_s is greater than 30 μC/cm² and lies in a direction tilted slightly from the major crystal surface. Switching, with fields perpendicular to the major crystal surface, occurs by a small ``rocking'' of this large P_s vector. The large component parallel to the major crystal surface can also be switched with high fields. Thus, there are four possible spontaneous polarization directions in the virgin crystal giving rise to complex domain structures.