Structural defects and non-ferroelectric piezoelectricity in an unpoled SrTiO3–Bi12TiO20 (ST–BT) composite ceramics

Anomalous piezoelectricity SrTiO3–Bi12TiO20 (ST–BT) composite ceramics fabricated by traditional sintering technology were first studied by positron annihilation lifetime spectroscopy and Doppler broadening spectroscopy. A large number of crystal defects were observed in ST–BT composite ceramics with the sintering temperature below 980 °C. The piezoelectric effect appeared concurrently with a high concentration of single-vacancy defects in the ceramics, suggesting that it may be closely related to the microstructure. This further proves that the flexoelectric effect is the origin of non-ferroelectric piezoelectricity.