Field assisted sintering of ceramic constituted by alumina and yttria stabilized zirconia

We show that a two-phase 50vol% 3YSZ-alumina ceramic flash-sinters at a furnace temperature of 1060°C under an electrical field of 150Vcm-1. In contrast undoped, single-phase alumina remains immune to field assisted sintering at fields up to 1000Vcm-1, although single-phase 3YSZ flash sinters at 750°C (furnace temperature). The mechanisms of field assisted sintering are divided into two regimes. At low fields the sintering rate increases gradually (FAST), while at high fields sintering occurs abruptly (FLASH). Interestingly, alumina/zirconia composites show a hybrid behavior such that early sintering occurs in FAST mode, which is then followed by flash-sintering. The specimens held in the flashed state, after they had sintered to near full density, show much higher rate of grain growth than in conventional experiments. These results are in contrast to earlier work where the rate of grain growth had been shown to be slower under weak electrical fields.