This study examined the situation of the densifying and microstructural change with various plate power levels, Ar flow rates, and translation rates of specimen and surveyed the optimal plasma sintering condition on the basis of those results. Also, sintering behaviors and microstructures of plasma sintered $Al_2O_3$ was compared with the conventionally sintered $Al_2O_3$. In addition, the effects of dopant, surface and pores of specimen on plasma sintering were studied.
Plasma sintering conditions of pure and MgO doped $Al_2O_3$ were 1.6~5.4 kW of plate powers, 1~5ℓ/min of Ar flow rates, and 1~4cm/min of translation rates of specimen.
As a result of plasma and conventional sintering of pure $Al_2O_3$ contenting the intentionally inserted pore in the bulk, abnormally grown grain was founded around the pore. It means that plasma was generated inside of the pore. Practically, plasma was generated at all of the pores, and local high temperature was obtained. Lattice diffusion was activated by this effect and sintering was accelerated.
Relative density and average grain size of plasma sintered pure $Al_2O_3$ at 3.6kW, 3cm/min, 2ℓ/min were 97% and 4.89㎛, respectively and in case of 0.1wt.% MgO doped $Al_2O_3$ sintered at 5.4kW 2cm/min, 3ℓ/min were 99%, 2.98㎛, respectively. On the other hand, conventionally sintered pure $Al_2O_3$ at 1600℃, 2hr were 98%, 5.8㎛ and MgO doped $Al_2O_3$ were 99%, 4㎛ respectively.
Consequently, microstructures obtained by plasma sintering process were more dense and fine microstructure than conventional sintering process and optimal plasma sintering condition of pure $Al_2O_3$ was 3~3.6kW of plate power, 2~3ℓ/min of Ar flow rate, 2~3cm/min of translation rate. In the case of MgO doped $Al_2O_3$, plate power of 5.4kW level was required because of the descent of temperature.
