First-principles study of ferroelectric, dielectric, and piezoelectric properties in the nitride perovskites CeBN3 ( B=Nb , Ta)

The nitride perovskite family has attracted widespread attention since the experimental synthesis of polar nitride perovskite LaWN₃. In this work, we investigated the ferroelectric, dielectric, and piezoelectric properties of two nitride perovskites CeBN₃ (B⁵⁺=Nb, Ta) using the first-principles calculation. Our results show that the polarization values of CeNbN₃ (CNN) and CeTaN₃ (CTN) approach those of typical perovskites LiNbO₃ and BaTiO₃, respectively. Interestingly, the A-site cation contributes significantly to the polarization of CNN and CTN, despite the lack of lone pair electrons in Ce⁴⁺. In addition, CTN and CNN exhibit unusually large static dielectric constants (>220) along the x direction, much larger than the y and z directions. This strong anisotropy primarily stems from the dominant infrared-active mode having a lower frequency or larger mode-effective charges along the x direction relative to the other two directions. Finally, we found both CTN and CNN have a comparatively large shear piezoelectric coefficient d₂₄ over 70 pC/cm². Our research provides insights for understanding the origin of ferroelectricity in nitride perovskites and their potential piezoelectric applications.