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

Abstract

The electrical responses of piezoelectric materials subjected to spherical microindentation are evaluated. Theoretical analysis based on normal indentation of a transversely isotropic, linear piezoelectric solid by a conducting steel sphere with zero potential bias is compared to experimental results. The materials considered are PZT-4 and (Ba_0.917Ca_0.083)TiO₃. Effects of poling, poling direction, indentation velocity, and polarization loss due to annealing were investigated. All the basic trends predicted by the theory are confirmed by the experiments. The current induced into the indentor due to the polarized layer on the contact surface of the piezoelectric specimen increases with time as the contact area increases. Experimentally, observed power dependence of current to indentation velocity is close to the theoretical value of 1.5. The relation between induced current and indentation time is specific to the properties of the material. It is demonstrated that in addition to some of the material constants, the poling direction and the aging behavior of piezoelectric ceramics can be determined by spherical indentation.