Synchrotron texture analysis of thick BiFeO3-PbTiO3 layers synthesised by tape casting using Aurivillius and non-Aurivillius templates

Abstract

The solid solution between bismuth ferrite and lead titanate (xBiFeO₃-(1-x)PbTiO₃ or BFPT) possesses a morphotropic phase boundary (MPB) between the rhombohedral and tetragonal forms at x=0.7. It is of interest to investigate the influence of field-driven rhombohedral-tetragonal phase transitions across the MPB, to determine whether correctly oriented BFPT can provide both giant piezoelectric properties and significant magnetoelectric coupling. Here, we used the reactive templated grain growth (RTGG) technique to prepare crystallographically textured 0.6BiFeO₃-0.4PbTiO₃ (60:40 BFPT) ceramics. Both Aurivillius structure templates (Bi₄Ti₃O₁₂ and PbBi₄Ti₄O₁₅) and perovskite templates (BaTiO₃ and SrTiO₃) were used to prepare textured 60:40BFPT. Synchrotron radiation experiments were used to determine the degree of texture. A current data suggests that only BaTiO₃ templates survive the sintering process, and other candidate template materials reacted with the 60:40BFPT matrix at high temperature. In the case of SrTiO₃, this reaction results in a low Curie temperature (T_c = 350°C) due to the substitution of Sr²⁺. Aurivillius templates resulted in high Curie temperatures (610°C) and may be chemically suitable if they could be stabilized during the sintering process. However, the resulting ceramics show low remanent polarization (P_r = 3 μc/cm²), while SrTiO₃ and BaTiO₃ templated ceramics show higher remanent polarizations of 36 and 30 μc/cm², respectively. Because of their high chemical stability in this system, BaTiO₃ templates appear to be the best candidate for fabricating textured BFPT by the TGG method, displaying a high degree of crystallographic texture.