Shock-Induced Transition in Barium Titanate

Measurements on BaTiO3 ceramic were made of inverse dielectric constant versus uniaxial strain for values of strain ranging between -0.0043 and -0.013. The strain was produced in the region behind a shock front generated in a slab of the material by impacting it with a flying plate. The plate was accelerated in a gas gun. The slabs were disks with electrodes on the flat surfaces. The normal stress producing these strains ranged between 8.5 and 26 kbars. The dielectric constant was obtained from oscillograms of the shock- induced depolarization current through a circuit connecting the electrodes. A straight line was fitted to the curve of inverse dielectric constant versus strain. The slope of the line was -0.11 plus or minus 0.04. Thermodynamic theory was used to calculate this slope assuming the material was in the paraelectric phase for the range of experimental shock pressures. The calculated value was -0.13. The calculated value is in agreement with the experimental value and the assumption that the material is in the paraelectric phase for shock pressures between 8.5 and 26 kbars.