Superior Piezoelectric Performance in Textured CaBi₂Nb₂O₉ Ferroelectric Ceramics through Rare-Earth Gadolinium Doping and Spark Plasma Sintering

Abstract

High-performance piezoelectric ceramics with excellent thermal stability are crucial for high-temperature piezoelectric sensor applications. However, conventional fabrication processes offer limited enhancements in piezoelectric performance. In this study, we achieved a significant breakthrough in the piezoelectric performance of highly textured CaBi 2 Nb 2 O 9 (CBN) ceramics by incorporating rare-earth gadolinium doping and utilizing spark plasma sintering. The resulting Ca 0.97 Gd 0.03 Bi 2 Nb 2 O 9 (CBN-3Gd) ceramics exhibited superior piezoelectric properties, with a high piezoelectric constant d 33 of 26 pC/N and a high Curie temperature T C of 946 °C. We employed piezoresponse force microscopy (PFM) to observe the morphology and dimensions of the ferroelectric domains, revealing a rod-shaped 3D domain configuration. This configuration facilitated polarization rotation in the textured ceramics, as analyzed using X-ray photoelectron spectroscopy (XPS) and polarization−electric field (P−E) hysteresis loops. Furthermore, the textured CBN-3Gd ceramics demonstrated exceptional thermal stability and reliability. The piezoelectric constant d 33 decreased by only 11.8% over a temperature range of room temperature to 500 °C, and the DC electrical resistivity remained at 6.7 × 10 5 Ω cm at 600 °C. This work not only highlights the great potential of textured CBN-based ceramics for high-temperature piezoelectric sensors but also provides a viable strategy for enhancing the performance of piezoelectric materials with large aspect ratio micromorphology. KEYWORDS: calcium bismuth niobate (CaBi 2 Nb 2 O 9 ), bismuth layer-structured ferroelectrics (BLSFs), high-temperature piezoelectric ceramics, textured ceramics, spark plasma sintering (SPS)