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 Ps 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 Ps 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.

Strain tuning of electronic structure inBi4Ti3O12−LaCoOChoi1, Lee2 2015Phys. Rev. B18120View full textAdd to dashboardCite

“…In this system, unlike conventional TMOs, E g of the system could be largely reduced (~1 eV) by changing the LCO substitution rate [12]. E g could be decreased as low as ~2.55 eV, while maintaining the strong ferroelectricity of BiT [13]. Since E g determines most of the electronic and optical characteristics of a material, the ability to tune E g provides an unprecedented pathway to developing TMOs with novel properties.…”

Optical anisotropy in bismuth titanate: An experimental and theoretical study

“…2,3 Dielectric, optical, and optoelectronic properties of BiT are of further interest in the area of optical memories since its band gap (E g $ 3.6 eV), 4 similar to most ferroelectric perovskite oxides, lies in the visible spectrum region. As a result, dielectric [5][6][7][8][9][10][11][12][13] and optical properties [13][14][15][16][17][18][19] of BiT have been extensively investigated for decades. In addition, there has been a renewed interest in the optical properties of ferroelectric BiT as noncentrosymmetric crystal structure of room temperature BiT could trigger asymmetric electron excitation, relaxation, and scattering leading to photovoltaic effect.…”

Wide bandgap tunability in complex transition metal oxides by site-specific substitution

“…Note that the c axis lattice constant of BiT is about eight times longer than that of usual simple perovskites. The ferroelectric polarization in BiT mainly points along the a axis direction 16 and is known to originate mostly from the perovskite sublayers, i.e., the shift of cations relative to O ions within the perovskite blocks 17,18 . One of the most attractive properties of this bismuth-layered material is its excellent sustainability of ferroelectricity even after intrusion of some oxygen vacancies 17 .…”