Bi4Ti3O12 Phase Research Articles

C-V CHARACTERISTICS OF Bi2Ti2O7 THIN FILMS ON n-Si(100)

We report the growth of Bi2Ti2O7 thin films on n type Si substrates by the chemical solution decomposition technique. Both the X-ray double-crystal diffraction and atomic force micro spectroscopy measurements are used to check the film properties. It is shown that the film is a multi crystal film dominated by the Bi2Ti2O7 phase. The C-V measurements are also performed on Au/Bi2Ti2O7/n-Si(100) MOS structure. It is revealed that both the fixed and mobile negative charges are contained in the film. The mobile negative charge results in the hysteresis loops on C-V curve.

Observation of Crystallization Process from Amorphous Bi4Ti3O12 Prepared by Rapid Quenching Method

We studied the crystallization of amorphous samples of Bi4Ti3O12 prepared by rapid quenching. Differential thermal analysis, powder X-ray diffraction and Raman spectral measurements revealed that the amorphous sample first crystallizes at approximately 610°C to a metastable Bi2Ti2O7 phase and then transforms irreversibly to the stable Bi4Ti3O12 phase at approximately 830°C.

Cation Disorder in Three-Layer Aurivillius Phases: Structural Studies of Bi2−xSr2+xTi1−xNb2+xO12 (0

The solid solutions Bi2−xSr2+xTi1−xNb2+xO12 (0<x<0.6). (1) and Bi4−xLaxTi3O12 (x=1 and 2) (2) have been analyzed in detail by a combination of powder X-ray and neutron diffraction. Both solid solutions adopt a tetragonal variant of the archetypal three-layer Aurivillius phase structure of the parent phase Bi4Ti3O12. The X-ray studies of (1) clearly show that, contrary to earlier assumptions, Sr2+ partially substitutes into the [Bi2O2] layers, even at the stoichiometric composition Bi2Sr2TiNb2O12, the maximum amount of substitution being about 30% at x=0.6. The neutron study demonstrates that the Sr2+ in this site adopts a significantly more isotropic coordination environment than Bi3+, thus stabilizing this unexpected disorder. The disorder is shown to be driven by the requirement for size matching of the fluorite-like and perovskite-like layers. A similar level of disorder is found in Bi2La2Ti3O12, and this is shown to be due to the requirements for optimum local coordination environment at the La3+/Bi3+ sites.

Effects of a Bi4Ti3O12 buffer layer on SrBi2Ta2O9 thin films prepared by the metalorganic decomposition

Ferroelectric SrBi2Ta2O9 thin films have been deposited on the Bi4Ti3O12 buffered Pt/Ti/SiO2/Si substrates using the metalorganic decomposition technique at annealing temperatures ranging from 600 to 750 °C. No pyrochlore phase was found in the SrBi2Ta2O9 thin films although the Bi2Ti2O7 phase appeared in the Bi4Ti3O12 buffer layers. A SrBi2Ta2O9 film with (200) predominant orientation was formed at 650 °C. The effects of the Bi4Ti3O12 buffer layer and post-annealing temperature on the structure, surface morphology, and electrical properties of SrBi2Ta2O9 thin films were analyzed.

Crystallization of Bi 4Ti 3O 12 from glasses in the system Bi 2O 3/TiO 2/B 2O 3

The system Bi 2O 3-TiO 2-B 2O 3 has a glass-forming region large compared to other ternary oxide systems, which energy the preparation of glasses possessing B 2O 3-contents as low as 25 mol%. During thermal treatment at temperatures in the range of 500 to 700°C, the ferroelectric Bi 4Ti 3O 12-phase is formed. In all compositions, after treatments at 600°C, a maximum crystal content is obtained. The variation of the glass composition affects the microstructure: the smaller the content of B 2O 3, the smaller are the crystallites formed and the larger their quantity. Some of these glass ceramics contain crystals with plate-like morphology. This morphology should enable the preparation of oriented glass ceramics by mechanical deformation processes, such as extruding.

Effects of O2 Gas Pressure in Heat Treatment on Surface Morphology and Electric Properties of Ferroelectric Bi4Ti3O12 Thin Films with c-Axis Orientation

Fabrication of ferroelectric Bi4Ti3O12 thin films was carried out by spin-coating pyrolysis of Bi and Ti naphthenates and successive heat treatment in O2 gas at various pressures. Heat treatment in O2 gas at high pressure was effective for the fabrication of c-axis oriented Bi4Ti3O12 thin films with a smooth surface and improvement of their electric properties. The thin film heat-treated at the O2 gas pressure of 4.0×105 Pa was a single phase of Bi4Ti3O12 completely oriented along the c-axis with good ferroelectric properties at room temperature: coercive field of 23 kV/cm, remanent polarization of 1.9 µ C/cm2, dielectric constant of 45, loss of 0.01 and leakage current density on the order of 10-9 A/cm2. The remanent polarization of the thin film was kept constant up to the polarization reversal at 1×107 cycles.

Fabrication of Ferroelectric Bi4Ti3O12 Thin Films by Dipping Pyrolysis of Metal Naphthenates and Micropatterns by an Electron Beam

Fabrication of ferroelectric Bi4Ti3O12 thin films was carried out by dipping pyrolysis of metal naphthenates. Single-phase Bi4Ti3O12 thin films with c-axis orientation perpendicular to the substrate surface were fabricated on Pt plates. They exhibited good ferroelectric properties: coercive field of 7.7 kV/cm and remanent polarization of 8.2 µ C/cm2. For the films fabricated on Pt/Ti/ SiO2/Si substrates, however, the Bi2Ti2O7 phase mainly grew because of Ti diffusion into the bismuth titanate layer during the heat treatment. Fine micropatterns with linewidth of less than 1 µ m in precursors of Bi4Ti3O12 were formed by spin-coating, irradiation with an electron beam and development. They were crystallized into the Bi4Ti3O12 phase by successive pyrolysis and annealing. The reaction between the metal naphthenate films and energized electrons was studied by IR spectroscopic analysis.

The influence of substrate temperature and annealing on phase formation and crystalline properties of bismuth titanate film by APMOCVD

Bismuth titanate thin films have been grown by the atmospheric pressure metal-organic chemical vapour deposition technique. The influences of substrate temperature and annealing on phase formation and crystalline properties have been studied. (100) oriented Bi4Ti3O12 films have been grown at 550 degrees C, while (001) preferred orientation films were obtained at high temperature (about 800 degrees C) annealing. At a temperature of 650-750 degrees C, a film with Bi4Ti3O12+Bi2Ti2O7 phases was formed. It is shown that the phase formation may depend upon the growth temperature and composition of film. The orientation of films mainly depended upon the lattice match with substrate.

Ferroelectric bismuth titanate films by hot wall metalorganic chemical vapor deposition

Ferroelectric bismuth titanate thin films were successfully deposited on Si, sapphire disks, and Pt/Ti/SiO2/Si substrates by hot wall metalorganic chemical vapor deposition. Triphenyl bismuth [Bi(C6H5)3] and titanium ethoxide [Ti(C2H5O)4] were used as the precursors. The deposition rates were in the range of 3.9–12.5 nm/min. The Bi/Ti ratio was easily controlled by precursor temperature, carrier gas flow rate, and deposition temperature. As-deposited films were pure Bi4Ti3O12 phase. The films were specular and showed uniform and fine grain size. Optical constants as a function of wavelength were calculated from the film transmission characteristics in the ultraviolet-visible-near infrared (UV-VIS-NIR) region. The 550 °C annealed film showed a spontaneous polarization of 26.5 μC/cm2 and a coercive field of 244.3 kV/cm.

Oxygen Ion Conductivity in a New Class of Layered Bismuth Oxide Compounds

AbstractCompounds that consist of intergrowths between the Aurivillius phase Bi4Ti3O12 and brownmillerite-like slabs of BaMO2.5were synthesized and their oxygen ion conductivities investigated. Both BaBi4Ti3ScO14.5 and BaBi4Ti3InO14.5 display a discontinuity in their Arrhenius plots that appears to be caused by an oxygen vacancy order-disorder transition. Conductivity data for two Aurivillius phases BaBi4Ti4O15 and BaBi2Nb2O9 are included for comparison.