Internal Stress and Phase Coexistence in Bismuth Ferrite-Lead Titanate Ceramics

The large range of tetragonal and rhombohedral phase coexistence in BiFeO
₃
-PbTiO
₃
slid solutions and the spontaneous disintegration of certain samples is investigated using X-ray diffraction. It is concluded that internal stress associated with the large spontaneous strain in the tetragonal phase is relieved by local transition to the lower volume rhombohedral phase. For larger grain sizes, microcracking provides an alternative route to stress relief.