It is expensive, however, and is an allergen to which some persons are sensitive. Zirconia is used primarily for its extreme inertness to most metals. Applications for fused or sintered zirconia include crucibles and furnace bricks. Transformation-toughened zirconia ceramics are among the strongest and toughest ceramics made. ZTA ceramics, which have lower density, better thermal shock resistance, and lower cost than the other two, are used in transportation equipment where they need to withstand corrosion, erosion, abrasion, and thermal shock.
Many engineering ceramics have multioxide crystalline phases.
Its low coefficient of thermal expansion is a necessary property for resistance to thermal fracture. They are composed of several oxides that form complex, multiphase microstructures. Glass ceramics do not have the strength-limiting porosity of conventional sintered ceramics. Properties can be tailored by control of the crystalline structure in the host glass matrix. Major applications are cooking vessels, tableware, smooth cooktops, and various technical products such as radomes.