Effect of heat-treatment mechanism on structural and electromechanical properties of eco-friendly (Bi, Ba)(Fe, Ti)O-3 piezoceramics

摘要

Lead-free piezoelectric ceramics, (Bi0.70Ba0.35)(Fe0.65Ti0.35)O-3 (BBFT), were fabricated via a solid-state reaction method and then treated using different heat-treatment processes (furnace cooling, air quenching (AQ), and water quenching). In all these ceramics, the X-ray diffraction analysis revealed morphotropic phase boundaries between the rhombohedral and tetragonal phases. Changes in the average grain size, relative density, and electrical properties in the BBFT-AQ composition were observed. For the optimum BBFT-AQ ceramic, significantly enhanced dynamic (d(33)* similar to 340 pm/V) and static (d(33) similar to 165 pC/N) piezoelectric coefficients were obtained. Moreover, the d(33)* increased to 40% (d(33)* similar to 475 pm/V) with increasing temperature from 25 degrees C to 75 degrees C upon the application of a 4.0 kV/mm electric field. The related defect states were established by the variation in the transition of Fe3+ to Fe2+ and O-V or V-O(center dot center dot) concentration observed using X-ray photoelectron spectroscopy analysis. These factors are directly related to the electromechanical response enhancement in the BBFT piezoceramics. This study provides a paradigm for a deeper analysis of particular scientific heat-treatment mechanisms and the enhancement of functional properties in BBFT ceramics.