Effect of the strength of an AC electric field compared to DC on the sintering rate and related grain size of zirconia (3Y-TZP)

The influence of the strength of an initial 60 Hz AC field Eo=1–50 V/cm on the sintering rate and corresponding grain size of yttria-stabilized zirconia (3Y-TZP) was determined and compared with an equivalent DC field. For both field types the sintering rate increased and the grain size decreased with field strength up to a critical value, beyond which no further effect occurred. The AC field however had a greater effect than the DC field over the entire field strength range. The major factor responsible for the enhanced sintering rate with both field types was concluded to be retardation of grain growth by the field. The retardation was in turn attributed to a reduction in the grain boundary energy by the interaction of the field with the space charge. Analysis of the results employing the absolute reaction rate theory gave magnitudes of the space charge potential and corresponding grain boundary energy in accord with reported values, but were larger with AC field than with DC. Factors which could contribute to the greater effect of an AC field compared to DC are suggested.