Production and Chemical Properties - Zirconia is produced by calcining zirconium compounds. - Zirconia has the chemical formula ZrO. - Its molar mass is 123.218 g/mol. - Zirconia appears as a white powder. - Zirconia is chemically unreactive. - It is slowly attacked by concentrated hydrofluoric acid and sulfuric acid. - It converts to zirconium carbide when heated with carbon. - In the presence of chlorine, it converts to zirconium(IV) chloride. - This conversion is used for the purification of zirconium metal.

Structure - Zirconia has three phases: monoclinic, tetragonal, and cubic. - The higher the temperature, the higher the symmetry of the structure. - The cubic phase can be stabilised by adding oxides of calcium or yttrium. - Monoclinic zirconia consists of seven-coordinated zirconium centers. - The mineral tazheranite is cubic and contains Zr, Ti, and Ca.

Engineering Properties - Zirconia undergoes phase changes from monoclinic to tetragonal to cubic. - The change in volume during these transitions can cause cracking. - Stabilised zirconia with dopants like yttria has superior properties. - Transformation toughening enhances fracture toughness. - Zirconia has a band gap dependent on its phase and preparation methods.

Uses - Zirconia is used in the production of hard ceramics. - It is used in dentistry for dental restorations and prostheses. - Zirconia is used in oxygen sensors and fuel cell membranes. - It is a precursor to lead zirconate titanate, a high-κ dielectric. - Zirconia is used as a thermal barrier coating in engines.

Applications, Properties, and Research - Zirconium dioxide is used in watch cases, gas tungsten arc welding electrodes, and thermal-barrier coatings for gas-turbine engines. - It is used in dental ceramics, kitchen knives, and tools. - Zirconium dioxide is four times harder than stainless steel. - It undergoes phase transformations during oxidation and exhibits transformation toughening. - Zirconium dioxide has various industrial and scientific applications, such as catalysts and photocatalysts. - Research has been conducted on the properties, machinability, and applications of zirconia ceramics. - Studies have been done on the phase transformation during oxidation of zirconium alloys and the toughening of zirconia through martensitic transformations. - Rapid prototyping and porcelain fused to zirconia prosthesis have been explored for dental applications.