A bismuth ferrite-based lead-free piezoelectric ceramic surpassing PZT-8 in thermal stability

Abstract

Piezoelectric materials are essential for electronics but suffer from thermal instability, especially lead-free alternatives to lead zirconate titanate (PZT). The absence of quantitative thermal stability metrics has hindered progress. In this work, we introduce a new index, denoted as "Sd", which accounts for both the operating temperature range and the central operating temperature, allowing for a comprehensive assessment. Applying this criterion, we found that the commercial PZT-4 material exhibits the highest thermal stability among the ceramics tested, confirming its reputation as the industry standard. Notably, we developed a new lead-free piezoelectric ceramic based on bismuth ferrite that achieved stable piezoelectric coefficient at 38‒247 °C, the corresponding Sd value (173) exceeds that (163) of commercial PZT-8 (20‒232 °C). Further analysis revealed that reducing the concentration of point defects improved its electrical homogeneity and reduced conductivity, leading to enhanced thermal stability. This work provides a new evaluation framework that can accelerate the development of thermally stable lead-free piezoelectric materials. The implications of this research extend beyond piezoelectrics, as the Sd index could find broader application in the characterization of other functional oxides.