In situ transmission electron microscopy study of the paraelectric to ferroelectric (cubic to tetragonal) phase transformation in lanthanum-modified lead titanate ceramics

Abstract

Lead titanate (PbTiO3) forms the ferroelectric end of the ferroelectric-antiferroelectric solid solution series PbTiO3-PbZrO3 (PZT), which is of considerable interest in various piezoelectric applications. Above the Curie point (TC), the material is cubic (paraelectric), point group m3m. Below this temperature transformation occurs to the tetragonal (ferroelectric) phase, point group 4mm. The strain generated in this transformation is relieved via the formation of twin-related structural (ferroelectric) domains. Lanthanum is added to polycrystalline lead titanate to aid in the poling operation (alignment of electric dipoles in individual grains via the application of a large electric field), through a reduction of the c/a ratio in the tetragonal phase. This transformation has been observed in this material in-situ via transmission electron microscopy (TEM).