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Zirconium Oxide

  <Zirconia Applications

Zirconium Oxide, ZrO₂ Ceramic Properties

Zirconia is an extremely refractory material. It offers chemical and corrosion inertness to temperatures well above the melting point of alumina. The material has low thermal conductivity. It is electrically conductive above 600°C and is used in oxygen sensor cells and as the susceptor (heater) in high temperature induction furnaces. With the attachment of platinum leads, nernst glowers used in spectrometers can be made as a light emitting filament which operates in air.

.Key Properties of Zirconium Oxide
	Use temperatures up to 2400°C
	High density
	Low thermal conductivity (20% that of alumina)
	Chemical inertness
	Resistance to molten metals
	Ionic electrical conduction
	Wear resistance
	High fracture toughness
	High hardness
. Typical Uses of ZrO2
	Precision ball valve balls and seats
	High density ball and pebble mill grinding media
	Rollers and guides for metal tube forming
	Thread and wire guides
	Hot metal extrusion dies
	Deep well down-hole valves and seats
	Powder compacting dies
	Marine pump seals and shaft guides
	Oxygen sensors
	High temperature induction furnace susceptors
	Fuel cell membranes
	Electric furnace heaters over 2000°C in oxidizing atmospheres

General Zirconium Oxide Information

Pure zirconia exists in three crystal phases at different temperatures. At very high temperatures (>2370°C) the material has a cubic structure. At intermediate temperatures (1170 to 2370°C) it has a tetragonal structure. At low temperatures (below 1170°C) the material transforms to the monoclinic structure. The transformation from tetragonal to monoclinic is rapid and is accompanied by a 3 to 5 percent volume increase that causes extensive cracking in the material. This behavior destroys the mechanical properties of fabricated components during cooling and makes pure zirconia useless for any structural or mechanical application. Several oxides which dissolve in the zirconia crystal structure can slow down or eliminate these crystal structure changes. Commonly used effective additives are MgO, CaO, and Y₂O₃. With sufficient amounts added, the high temperature cubic structure can be maintained to room temperature. Cubic stabilized zirconia is a useful refractory and technical ceramic material because it does not go through destructive phase transitions during heating and cooling.

The controlled, stress induced volume expansion of the tetragonal to monoclinic inversion is used to produce very high strength, hard, tough varieties of zirconia available from Accuratus for mechanical and structural applications. There are several different mechanisms that lead to strengthening and toughness in zirconias that contain tetragonal grains. This is a complex subject matter. Simplistically, these depend on the grain sizes, the thermal history and the kind and amount of stabilizing additive in the body. These variations lead to two strong, commercially available partially stabilized zirconia  (PSZ) microstructures identified as TTZ (tetragonally toughened zirconia) and TZP (tetragonal zirconia polycrystal) ceramics. The TTZ is an MgO partially stabilized zirconia often designated MgTTZ or MgPSZ consisting of uniformly dispersed tetragonal precipitates in larger cubic phase crystals. The secondary thermal aging process requiring tight manufacturing controls for proper microstructural development has limited the supplier base for the tetragonally toughened zirconias.  The second variety, TZP, is a pure tetragonal phase, very fine grain material stabilized with rare earth oxides, primarily yttria and less commonly ceria. They are often designated YTZP for the yttria stabilized product and CeTZP for the ceria stabilized product.  The TZP material has found uses in cutting and wear resistant applications due to its reliable and outstanding hardness and toughness. TZP properties degrade rapidly when the material is exposed to water vapor at 200 to 300°C, so controlled use conditions are important for good performance. All of the toughened zirconias show a degrading of properties with increasing temperature, and this class of high strength, tough materials is generally limited to use temperatures below 800°C

Download YTZP Zirconia datasheet

Engineering Properties of Toughened Zirconia*

*All properties are room temperature values except as noted.
The data presented is typical of commercially available material and is offered for comparative purposes only. The information is not to be interpreted as absolute material properties nor does it constitute a representation or warranty for which we assume legal liability. User shall determine suitability of the material for the intended use and assumes all risk and liability whatsoever in connection therewith.

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