Studies on the nano spinel addition effect on zirconia properties

Abstract

Zirconia has recently attracted a significant attention in fabrication of various kinds of functional and structural ceramics that are widely used in high tech applications such as fuel cells, oxygen sensors, cutting blades, grinding media, knives, and ceramic bearing hip replacement. It is a polymorphic material that exists in three phases: monoclinic, tetragonal, and cubic allotropes. Upon cooling down from high-temperatures, the tetragonal-monoclinic martensitic transformation gives rise to a volume expansion of ~ 3-4%. Such large volume expansion causes large stresses, which could induce micro-cracking leading to mechanical failure. In this study commercial monoclinic zirconia was fully stabilized in the cubic form at room temperature through magnesium aluminate spinel (MA), magnesium aluminate spinel with excess magnesia (MR) and magnesium aluminate spinel with excess alumina (AR) addition to protect zirconia composite ceramics from failure. Despite the good properties as well as compatibility of MA with zirconia ceramic systems, effect of MA addition on densification and stabilization of raw m-ZrO2 has not been well studied yet. In this context, this investigation was designed; firstly, to illustrate the effect of MA addition on the stabilization and densification properties of zirconia ceramics, and secondly, to