A realization of excellent piezoelectricity and good thermal stability in CaBi 2 Nb 2 O 9 : Pseudo phase boundary

Phase boundaries (PBs) are known to contribute to the outstanding performances of lead‐based and lead‐free materials. However, a lack of PBs restricts the promotion of piezoelectric performance in bismuth layer‐structured ferroelectrics (BLSFs). In this work, a pseudo PB, ie, pseudotetragonal distortion (regulated by Ce), is proposed to promote the piezoelectric properties of CaBi 2 Nb 2 O 9 ‐based ceramics, and an excellent piezoelectric constant ( d 33 ) of 20.2 pC/N with a high Curie temperature of 923°C is obtained. Verified Ce incorporation into the (Bi 2 O 2 ) 2+ layer alters the environment of the (Bi 2 O 2 ) 2+ layer, thereby influencing the atomic displacement in the Nb‐O octahedron and modulating the theoretical spontaneous polarization ( P s ). Strengthening of the pseudotetragonal distortion is favorable to the polarization switching, and maintains the theoretical P s of ceramics at a high level, thus realizing the promotion of d 33 . Furthermore, pseudotetragonal distortion guarantees good thermal depoling performance of the ceramic, which remains at 89.6% (18.1 pC/N) of its initial d 33 after depoling at 875°C. This work provides clear guidance on obtaining high d 33 and good thermal stability in BLSFs.