Zirkonia

Zirkonia, chemically zirconium dioxide (ZrO2), is a ceramic material widely used for its mechanical strength and aesthetic properties. In its natural form it is monoclinic at room temperature, but when processed as a ceramic it is usually stabilized in tetragonal or cubic phases by adding stabilizers such as yttria (Y2O3) or magnesia (MgO). The term zirconia covers both the polycrystalline ceramic and the stabilized variants used in industry and medicine.

The most common stabilized form is yttria-stabilized zirconia (YSZ), which leverages a tetragonal phase that, under stress, undergoes a transformation to monoclinic and dissipates energy, increasing fracture toughness. This transformation toughening makes YSZ tougher than many other ceramics. Zirconia is resistant to corrosion, has high hardness, and good wear resistance. It is radiopaque and exhibits relatively low thermal conductivity and low thermal expansion.

Two major groups of applications are dental restorations and jewelry. In dentistry, zirconia is used for crowns, bridges, abutments, and implants, often as monolithic units or layered with porcelain; its tooth-like color and biocompatibility are advantages. In jewelry, cubic zirconia (CZ) is a synthetic gemstone with a cubic crystal structure used as a diamond substitute. Zirconia ceramics also find use in engineering components and, in some forms, in solid oxide fuel cells and oxygen sensors.

Processing typically involves synthesizing stabilized zirconia powders, forming them by pressing or CAD/CAM methods, and sintering at high temperature. Finishing and glazing are common in dental applications. Aging, or low-temperature degradation, can occur in humid environments, especially for high-purity tetragonal zirconia; stabilization and surface treatments help mitigate this risk. Overall, zirconia combines strength, toughness, and aesthetics, making it a versatile material in technical and medical fields.