By adding small percentages of yttria, these phase changes are eliminated, and the resulting material has superior thermal, mechanical, and electrical properties.

This mechanism, known as transformation toughening, significantly extends the reliability and lifetime of products made with stabilized zirconia.

[6][7] The ZrO2 band gap is dependent on the phase (cubic, tetragonal, monoclinic, or amorphous) and preparation methods, with typical estimates from 5–7 eV.

When ZrO₂ is stabilised by adding 3 mol% of yttrium oxide (3Y-ZrO₂) at high temperatures (~1500 °C), its mechanical properties such as fracture toughness, flexural strength, and hardness are significantly improved.

In contrast, when ZrO₂ is stabilised with 5 mol% of yttrium oxide (5Y-ZrO₂), it is primarily in the cubic phase, and does not undergo transformation toughening mechanism when stress is applied.

[9][10] The main use of zirconia is in the production of hard ceramics, such as in dentistry,[11] with other uses including as a protective coating on particles of titanium dioxide pigments,[2] as a refractory material, in insulation, abrasives, and enamels.

Zirconia is a precursor to the electroceramic lead zirconate titanate (PZT), which is a high-κ dielectric, which is found in myriad components.

Another low-thermal-conductivity use is as a ceramic fiber insulation for crystal growth furnaces, fuel-cell stacks, and infrared heating systems.

This material is also used in dentistry in the manufacture of subframes for the construction of dental restorations such as crowns and bridges, which are then veneered with a conventional feldspathic porcelain for aesthetic reasons, or of strong, extremely durable dental prostheses constructed entirely from monolithic zirconia, with limited but constantly improving aesthetics.

Some studies demonstrated the activity of doped zirconia (in order to increase visible light absorption) in degrading organic compounds[22][23] and reducing Cr(VI) from wastewaters.

Zirconia is also employed in the deposition of optical coatings; it is a high-index material usable from the near-UV to the mid-IR, due to its low absorption in this spectral region.

[26] In 2015 Omega released a fully ZrO2 watch named "The Dark Side of The Moon"[27] with ceramic case, bezel, pushers, and clasp, advertising it as four times harder than stainless steel and therefore much more resistant to scratches during everyday use.