INVESTIGATION OF TETRAGONAL DISTORTION IN THE PBTIO3 BIFEO3 SYSTEM BY HIGH-TEMPERATURE X-RAY-DIFFRACTION

Compositions in the (Pb1-xBix) (Ti1-xFex)O-3 solid solution system for x less than or equal to 0.7 show unusually large tetragonal distortion. High-temperature x-ray diffraction was used to study the tetragonal distortion as a function of temperature (25-700 degrees C) for compositions (x = 0-0.7) using powders prepared by solid-state reaction in the above system. Large changes in the lattice parameters were observed over a narrow temperature range near Curie temperature (T-C) for compositions near the morphotropic phase boundary (MPB) (x similar or equal to 0.7) Compositions near MPB showed a c/a ratio of 1.18 at room temperature. Polar plots of lattice constants at different temperatures indicated strong anisotropic thermal expansion with zero thermal expansion along the [201] direction.