Role of small amount of MgO and $ZrO_{2}$ on creep behaviour of high purity $Al_{2}O_{3}$

Small levels of various dopants have a significant effect on creep in polycrystalline alumina. While most previous studies have examined the effect of ionic size, the influence of valency of dopants on creep hasnot yet been completely characterized. The present detailed experimental study, utilizing magnesia and zirconia with a similar ionic size, demonstrates that the ionic valency of dopants also plays a crucial role in creep since magnesia does not significantly alter creep whereas zirconia retards creep substantially. Magnesia doped aluminade forms by Coble diffusion creep where as zirconia doped alumina deforms by an interface controlled diffusion creep process