Zirconium

   Zirconium (Zr) is a shiny, grayish-white metal with a high melting point of 1855°C and boiling point of 4377°C. It has a density of 6.52 g/cm3 and shows decent resistance to corrosion. On the Mohs hardness scale, zirconium scores around 5, exhibiting good ductility and malleability as well.

  A common zirconium compound is zirconium dioxide (ZrO2), also called zirconia, which has an even higher 2715°C melting point and exceptional chemical attack resistance. As a refractory material with a thermal expansion coefficient close to silicon at 10.5 × 10^-6 K^-1, zirconia works well in foundry molds and crucibles.

For applications, zirconium metal itself is popular in nuclear reactors because of its low neutron-capture cross-section and corrosion resistance against hot water. Additionally, zirconium alloys are utilized for fuel cladding in nuclear reactors since they minimize neutron absorption and retain strength at high temperatures.

In dentistry, zirconia is widely applied in dental implants and crowns due to its biocompatibility and mechanical performance. In ceramics, zirconia acts as a crucial component thanks to its high crack propagation resistance that enables strong, durable products.

Furthermore, zirconia finds use in oxygen sensors and fuel cell membranes because of its ionic conductivity - the ability to allow oxygen ions to move freely at high temperatures.