Bi2Ti2O7: It Is Not What You Have Read

Coprecipitation synthesis methods followed by microwave sintering techniques were utilized to obtain dense phase pure Bi2Ti2O7 polycrystalline ceramic pellets. No evidence of secondary phases was found in the powder or pellets. This maiden achievement allowed for primary thermophysical, crystallographic, and dielectric characterization of this ceramic compound. Density functional theory was used to model the structure of the pyrochlore, from which the theoretical X-ray diffraction pattern was obtained to determine the purity of the experimental compound. Discrepancies among reports in literature regarding the structure, stability, and supposed ferroelectricity of this material are discussed and clarified. A modification to the phase diagram of the Bi2O3-TiO2 system is proposed based on the results of the present investigation. In addition, and contrary to prior reports, the dielectric characterization of Bi2Ti2O7 reveals a linear dielectric with high permittivity values at room temperature (115 at 500 kHz), and more remarkably, a temperature and frequency dependent dielectric relaxation.