Growth of Ca, Zr co-doped BaTiO3 lead-free ferroelectric single crystal and its room-temperature piezoelectricity

Donglin Liu,Yue Sun,Qingfen Yan,Qiang Li,Jaeshik Shim

doi:10.1063/1.4994764

Abstract

Lead-free Ca, Zr co-doped BaTiO3 (BCZT) single crystal with a dimension up to 2mm×2mm×2mm was grown by a spontaneous nucleation technique using KF as the flux. The composition of the studied single crystal was defined to be Ba0.798Ca0.202Zr0.006Ti0.994O3, corresponding to a tetragonal phase at room temperature. The &lt;001&gt; oriented single crystal exhibited a quasi-static piezoelectric constant of approximately 232 pC/N. The effective piezoelectric coefficient d33* of the single domain crystal obtained under a unipolar electric field of 35 kV/cm was 179 pm/V. Rayleigh analysis was used to identify the intrinsic and extrinsic contributions to the room-temperature piezoelectricity of BCZT single crystal. The extrinsic contribution was estimated up to 40% due to the irreversible domain wall movement. Furthermore a sixth-order polynomial of Landau expansion was employed to analyze the intrinsic contribution to piezoelectricity of BCZT single crystal. The large energy barriers inhibited polarization rotations, leading to the relatively low piezoelectricity.

Highlights

For more than half a century, the lead-based piezoelectric materials have been of great importance in sensors, actuators, transducers, and energy harvesters.[1,2] the lead-based piezoelectric materials are facing a global restriction due to the toxicity of lead despite their outstanding piezoelectricity.[3,4] the lead-based piezoelectric materials can not satisfy the need of transducers for underwater applications due to the high acoustical impedance.[5]
Most lead-free piezoelectric materials have inferior piezoelectricity compared to lead-based materials, e.g., (K,Na)NbO3 (KNN) based ferroelectrics have the longitudinal piezoelectric coefficient (d33) of about 400 pC/N6–8 and (Na,Bi)TiO3 (NBT) based ferroelectrics have a d33 of about 200∼500 pC/N.7,9
In 2009, Ren et al.[10] reported Ba(Zr0.2Ti0.8)O3-(Ba0.7Ca0.3)TiO3 (BZT-BCT or BCZT) piezoceramics with a d33 of 620 pC/N at the morphotropic phase boundary (MPB), which is comparable with the PZT piezoceramics

Summary

Introduction

For more than half a century, the lead-based piezoelectric materials have been of great importance in sensors, actuators, transducers, and energy harvesters.[1,2] the lead-based piezoelectric materials are facing a global restriction due to the toxicity of lead despite their outstanding piezoelectricity.[3,4] the lead-based piezoelectric materials can not satisfy the need of transducers for underwater applications due to the high acoustical impedance.[5]. Growth of Ca, Zr co-doped BaTiO3 lead-free ferroelectric single crystal and its room-temperature piezoelectricity In 2012, Zheng et al grew the BCZT single crystal by the Czochralski method in a mixed flux of TiO2 and ZrO2.11 The Curie temperature of the as-grown crystal was below 0 ◦C and the phase structure was cubic at room temperature.

Results

Conclusion