A simple Bi3+ self-doping strategy constructing pseudo-tetragonal phase boundary to enhance electrical properties in CaBi2Nb2O9 high-temperature piezoceramics

Calcium bismuth niobate (CaBi2Nb2O9, CBN)-based ceramics are promising candidates for high temperature application, the electrical properties of which are commonly enhanced by complex ion substitution or texture processes. Here, we report that high piezoelectricity and high resistivity were achieved in Ca1-xBi2+xNb2O9 by constructing pseudo-tetragonal boundary through a simple strategy of Bi3+ self-doping. At the pseudo-tetragonal boundary, Ca0.96Bi2.04Nb2O9 ceramics maintain high Curie temperature Tc = 942 °C, and show high piezoelectric coefficient d33 = 15.1 pC/N and high resistivity ρdc = 2 × 106 Ω cm (@600 °C). It is proved that the good piezoelectric property mainly originates from the increase of domain density. In addition, Ca0.96Bi2.04Nb2O9 ceramics reveal good thermal depoling performance, remaining 90% of piezoelectricity after thermal depoling at 900 ℃, which is due to small thermal expansion and structural distortion. Our work provides a promising candidate for high temperature applications and an easy way to improve the performance of Aurivillius-type piezoelectric ceramics.