Fatigue and high temperature behaviour of the La-doped bismuth-ferrite lead-titanate system

For the past fifty years, lead zirconate titanate (PZT) has been the material of choice for the piezoelectric industry with piezoelectric materials showing promise in their applicability to smart devices and structures, from adaptive optics to ultrasonics and sonar. The longevity
and reliability of PZT is, as with any commercial material, a topic that is well documented with reported operating lifetimes as large as 109 cycles. However PZT is severely limited in the type of thermal environment it can sustainably operate in, with maximum operating temperatures conservatively set around 150°C for commercial materials a new material is required for use in thermally hostile environments.
The basic aim of this research was to investigate the performance of 3% La-doped BFPT as a device at high temperatures, fields and stresses in comparison to equivalent PZT materials and further understanding of fatigue in both materials - essential for use of either as a
commercially viable device. As no such, readily accessible, apparatus for testing ferroelectric ceramics existed it was essential to first develop the capability before experimentation could begin.
Upon development of a suitable apparatus, BFLPT and PZT fatigue studies were conducted and the fatigue as a function of domain contributions investigated using weak-signal measurements in bulk materials. Furthermore, using weak-signal measurements a study of domain behaviour at temperature was sought to give insight into the fundamental behaviour of ferroelectric materials at elevated temperatures - something previously only investigated using the likes of synchrotron facilities, and highlighted previously unobserved contribution changes occurring during material ageing.