Electrical response during indentation of piezoelectric materials: A new method for material characterization

The electrical responses of piezoelectric materials subjected to spherical microindentation are evaluated. Theoretical analysis based on normal indent ation of a transversely isotropic, linear piezoelectric solid by a conducti ng steel sphere with zero potential bias is compared to experimental result s. The materials considered are PZT-4 and (Ba0.917Ca0.083)TiO3. Effects of poling, poling direction, indentation velocity, and polarization loss due t o annealing were investigated. All the basic trends predicted by the theory are confirmed by the experiments. The current induced into the indentor du e to the polarized layer on the contact surface of the piezoelectric specim en increases with time as the contact area increases. Experimentally, obser ved power dependence of current to indentation velocity is close to the the oretical value of 1.5. The relation between induced current and indentation time is specific to the properties of the material. It is demonstrated tha t in addition to some of the material constants, the poling direction and t he aging behavior of piezoelectric ceramics can be determined by spherical indentation. (C) 1999 American Institute of Physics. [S0021-8979(99)08401-7 ].