 Zirconium dioxide ZrO2 |
| Sometimes known as zirconia, is a white crystalline oxide of zirconium. Its most naturally occurring form, with a monoclinic
crystalline structure, is the rare mineral, baddeleyite. The high temperature cubic crystalline form, called 'cubic zirconia',
is rarely, if ever, found in nature, but is synthesized in various colours for use as a gemstone and is the best-known diamond
simulant.
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| Zirconium dioxide is one of the most studied ceramic materials. Pure ZrO2 has a monoclinic crystal structure at room temperature and transitions to tetragonal and cubic at increasing temperatures.
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| It is used as a refractory material, in insulation, abrasives, enamels and glazes. Stabilized zirconia is used in oxygen sensors and fuel cell membranes because it has a unique ability to allow oxygen ions to move freely through the crystal structure
at high temperatures. This high ionic conductivity (and a low electronic conductivity) makes it one of the most useful electroceramics.
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| Zirconia is one of few compounds that actually becomes conductive at high temperatures, and more conductive, as its temperature
increases. Zirconia starts out with a very high resistance at room temperature, greater than 1 trillion ohm-cm. As the temperature
increases it has less than 20,000 ohm-cm at 500 degrees Celsius, to having less than 1,000 ohm-cm of resistance at 1,000 degrees
Celsius. It loses nearly all of its resistance around 2,000 degrees Celsius, and becomes a very good conductor.
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