The purpose of this investigation was to conduct a crystallographic study of the PbZrO₃-PbTiO₃-BiFeO₃ ternary system, where all three components are perovskites. Lead zirconate is antiferroelectric, lead titanate is ferroelectric, and bismuth ferrate is thought to be ferroelectric. X-ray diffraction analysis was employed to determine the crystallographic structure and lattice parameters.
A tetragonal region was found to exist in the area of high PbTiO₃ content. A rhombohedral region occurred in the remainder of the system with high BiFeO₃ and PbZrO₃ content, except for an orthorhombic envelope along the PbZrO₃-BiFeO₃ side of the diagram up to approximately 70 per cent BiFeO₃.The phase boundaries in the system had a phase width, rather than being distinct lines.
The addition of PbZrO₃ to the binary PbTiO₃-BiFeO₃ suppresses the normally increasing c/a ratio which occurs as the BiFeO₃ content is increased. At 50 PbZrO₃:5O PbTiO₃, the addition of BiFeO₃ decreases this ratio.
The orthorhombic region near the PbTiO₃-BiFeO₃ binary was indexed using a multiple-cell orthorhombic structure. All three lattice parameters decreased with additions of BiFeO₃.
High resolution conditions on the diffractometer were required to determine the peak splitting on most of the rhombohedral x-ray patterns. The rhombohedral distortion increased and the a parameter decreased with increasing BiFeO₃ content.
The dielectric constant and Curie point were determined for various ratios of BiFeO₃ and 50 PbZrO₃ :50 PbTiO₃. The Curie point was found to be 380 and 400°C for 20 and 30 per cent BiFeO₃, respectively. For 20 per cent BiFeO₃, a dielectric constant of 685 was ascertained. The present study finds significantly higher electrical properties than those reported previously --Abstract, pages ii-iii
