Electric-Field-Induced Phase Transformation and Frequency-Dependent Behavior of Bismuth Sodium Titanate-Barium Titanate.

Kai-Yang Lee,Jens Winter,Lucas Lemos Da Silva,Daniela Seifert,Nitish Kumar,Manuel Hinterstein,Stefano Checchia,Martin Etter,Xi Shi,Mark Hoffman

doi:10.3390/ma13051054

Abstract

The electric field response of the lead-free solid solution (1−x)Bi0.53Na0.47TiO3–xBaTiO3 (BNT–BT) in the higher BT composition range with x = 0.12 was investigated using in situ synchrotron X-ray powder diffraction. An introduced Bi-excess non-stoichiometry caused an extended morphotropic phase boundary, leading to an unexpected fully reversible relaxor to ferroelectric (R–FE) phase transformation behavior. By varying the field frequency in a broad range from 10−4 up to 102 Hz, BNT–12BT showed a frequency-dependent gradual suppression of the field induced ferroelectric phase transformation in favor of the relaxor state. A frequency triggered self-heating within the sample was found and the temperature increase exponentially correlated with the field frequency. The effects of a lowered phase transformation temperature TR–FE, caused by the non-stoichiometric composition, were observed in the experimental setup of the freestanding sample. This frequency-dependent investigation of an R–FE phase transformation is unlike previous macroscopic studies, in which heat dissipating metal contacts are used.

Highlights

Piezoelectric materials exhibit the property of converting electrical energy into mechanical energy and vice versa
Based on dielectric and piezoelectric property measurements, this study presents a temperature-composition phase diagram with a morphotropic phase boundary (MPB), separating the rhombohedral bismuth sodium titanate (BNT) and the tetragonal barium titanate (BT) phase, at compositions with about 6%–7% BT [9]
The different behavior of coexisting phases could be confirmed by in situ experiments on BNT-based compositions by Hinterstein et al [9,12]. These findings indicate an analogy to “relaxor ferroelectrics”, a designation made common by Cross [12,13,14]

Summary

Introduction

Piezoelectric materials exhibit the property of converting electrical energy into mechanical energy and vice versa. This feature is required in a broad range of devices, such as actuators, transducers, sensors, nano-positioners, ultrasonic motors, imaging devices, and other applications [1]. Lead and lead oxide (PbO) are both found to be hazardous for human health and the environment [4]. Due to the rapidly increasing amount of electrical and electronic waste, the European Waste Electrical and Electronic Equipment Directive (WEEE) / Restriction of Hazardous Substances (RoHS) was adopted by the EU parliament, in order to protect human health and environment from toxic and harmful substances [5]

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Results

Conclusion