Preparation of poled, twin-free crystals of ferroelectric bismuth tttanate, Bi4Ti3O12

Abstract
Twinning involving interchange of the a- and b-axis directions in ferroelectric bismuth titanate, Bi4Ti3O12, can be eliminated by annealing the crystals through the Curie transition in an appropriate thermal gradient. The crystals can be poled at a temperature just below the Curie transition by the application of pulsed electric fields, using a suitable electrode configuration. The techniques employed permitted the application of fields up to 30 kv/cm to crystals with resistivities of the order of 103 ohm cm. The transition at the Curie point from monoclinic to tetragonal symmetry is complex, and appears to occur in at least two stages.