Electrical response of BaTiO3 ceramics to the shock-induced ferroelectric-paraelectric transition

Abstract

The electrical response of BaTiO3 ceramics to the strong shock compression well above the Hugoniot-elastic limit or ferroelectric-paraelectric transition pressure is studied to separate and identify the causes of shock-induced electrical response of ferroelectric materials. Measurements of voltage and current histories under shock compression are performed by using poled and nonpoled specimens, assemblies of both parallel and normal modes, and explosive systems. In order to consider the effects due to elastic-plastic deformation and shock-induced conduction, the Hugoniot compression curve and electrical conductivities are also measured by using nonpoled specimens. The Hugoniot-elastic limit stress is determined to be 4.8–6.4 GPa for porous specimens with 1.7–4.4% porosity, and the shock velocity (Us) and particle velocity (Up) Hugoniot can be closely described as Us =4.29+1.66Up km/s in the plastic region. The electrical conductivity values at 12- and 29-GPa peak stresses are measured to be 2.1×10−3 and 4.8×10−2 S/cm, respectively. Both voltage histories for the parallel and normal modes at 12- and 29-GPa peak stresses show similarly increasing signals with time. Although the signals of the 29-GPa peak stress show large internal losses due to shock-induced conduction, these signals are reasonably analyzed by a simple analytical model based on the ferroelectric-paraelectric transition. The relative dielectric constant values under shock compression calculated by the model from the measured voltage histories are in the range (5–71)×103, which is consistent with those measured under static compression. Current histories for the parallel and normal modes at the 12-GPa peak stress show a pulse-shaped signal and a constant-current-shaped signal, respectively, whose total integrated charges are in agreement with those due to the initial remanent polarization, with the losses less than 20%. It is concluded that the measured electrical responses of poled BaTiO3 ceramics to the shock compression well above the Hugoniot-elastic limit are caused not by piezoelectricity, but chiefly by the shock-induced ferroelectric-paraelectric transition, in this study.