Fracture toughness of BaTiO3 and BaTiO3-Al2O3 composite under electric field

In order to investigate the effect of electric polarization on fracture toughness of monolithic BaTiO3 and 5 mol% BaTiO3-Al2O3 composite (5B95A), indentation fracture tests were conducted on unpoled and poled samples under various applied electric fields. From the results, it is found that applied electric fields can increase or decrease fracture toughness in both monolithic BaTiO3 and 5B95A composite depending on direction of electric field. For unpoled and poled samples under the positive (in the same direction to the poling direction), fracture toughness parallel to the poling direction increased, while that perpendicular to the poling direction decreased. Under the negative (in the opposite direction to the poling direction), fracture toughnesses both parallel and perpendicular to the poling direction for poled monolithic BaTiO3 and 5B95A composite were decreased with increasing applied electric field. This behavior of 5B95A composite was consistent with that of monolithic BaTiO3. It was concluded that polarization switching of piezoelectric BaTiO3 particles phase under electric fields has a significant influence on fracture toughness of the present composite.