Understanding the piezoelectric origin of bismuth layer-structured ferroelectric polycrystal using first-principle method

Polycrystalline ferroelectric piezoelectric materials are widely used in various functional electronic devices. We present a systematic orientational average method to estimate the piezoelectric properties of ferroelectric polycrystals via first-principle calculations. This method can construct a bridge to connect the monocrystalline and polycrystalline ferroelectric piezoelectric materials, which opens a door to estimate the piezoelectric properties of polycrystals via first-principle calculations, helping the further study of piezoelectric polycrystals. The piezoelectric properties of bismuth layer-structured ferroelectrics (BLSFs) polycrystals are investigated via the method, which presents a good agreement in other theoretical and experimental results. It is found that the longitudinal polarization stretching and in-plane polarization rotation contribute the most of piezoelectricity for poled polycrystals. Unexpected polarization stretching of Bi2O2 layer and slipping between Bi2O2 layer and perovskite block are revealed, being considered to play an important role for the piezoelectricity of BLSFs.