Introduction

ZrO₂ is a technologically important material. It possesses many desirable characteristics such as a high melting point, resistance to oxidation, low thermal conductivity, high coefficient of thermal expansion and high hardness. Bulk ZrO₂ has three equilibrium solid phases: monoclinic below 1100°C, face-centered cubic at temperatures above 2370°C and tetragonal between these temperatures [1]. The tetragonal phase has been the focus of much research due to a phase transformation toughening mechanism whereby the tetragonal phase transforms to monoclinic in a stress field with subsequent dissipation of the detrimental energy. The cubic and tetragonal phases of ZrO₂ can be stabilized down to room temperature with suitable dopants such as yttria and magnesia, which has led to a great deal of research in the area of doped zirconia films [2-4]. The increased fracture toughness of stabilized ZrO₂ has led to its application as a thermal barrier coating on gas turbines [5] and produced great potential for other advanced material applications. Research has also been conducted which focuses on phase transformation and stabilization of pure ZrO₂ [6-8].