Electric field Induced phase transformation In ceramics

It is known that: (1) an analogy exists between the electrical and mechanical properties of dielectric materials, (2) the polarization energy can be dissipated via phase transitions, and (3) phase transformation produced in ceramics under mechanical stress or at the time of crack propagation, increases fracture toughness. The influence of an electric field on the structure of an alumina (AI/sub 2/O/sub 3/) ceramic, with ZrO/sub 2/ (20%) is reported. It is shown that: (a) the percentage of ZrO/sub 2/ undergoing phase transformation from tetragonal to monolithic (t-->m) depends on the amplitude and duration of the applied electric field, (b) the phase transformation plays a dominant role on the conditionning of the insulator, (c) the sintering method influences the (t-->m) rate. The results presented will provide original insights into the conditioning mechanism, partial discharge mechanism, flashover, and on the role of internal stresses on voltage withstand of dielecrics.