| | Zirconium Oxide, ZrO2 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 Back to top Engineering Properties
of Toughened Zirconia* | Zirconium Oxide, Y2O3 stabilized TZP | | Mechanical | SI/Metric (Imperial) | SI/Metric | (Imperial) | | Density | gm/cc (lb/ft3) | 6 | (205.4) | | Porosity | % (%) | 0 | (0) | | Color | — | ivory | — | | Flexural Strength | MPa (lb/in2x103) | 900 | (120.4) | | Elastic Modulus | GPa (lb/in2x106) | 200 | (45) | | Shear Modulus | GPa (lb/in2x106) | — | — | | Bulk Modulus | GPa (lb/in2x106) | — | — | | Poisson’s Ratio | — | — | — | | Compressive Strength | MPa (lb/in2x103) | — | — | | Hardness | Kg/mm2 | 1300 | — | | Fracture Toughness KIC | MPa•m1/2 | 13 | — | Maximum Use Temperature
(no load) | °C (°F) | 1500 | (2730) | | Thermal | | | | | Thermal Conductivity | W/m•°K (BTU•in/ft2•hr•°F) | 2 | (13.9) | | Coefficient of Thermal Expansion | 10–6/°C (10–6/°F) | 10.3 | (5.7) | | Specific Heat | J/Kg•°K (Btu/lb•°F) | — | — | | Electrical | | | | | Dielectric Strength | ac-kv/mm (volts/mil) | — | — | | Dielectric Constant | — | — | — | | Dissipation Factor | — | — | — | | Loss Tangent | — | — | — | | Volume Resistivity | ohm•cm | >1010 | — | | Zirconium Oxide, MgO stabilized
TTZ | | Mechanical | SI/Metric (Imperial) | SI/Metric | (Imperial) | | Density | gm/cc (lb/ft3) | 5.5 | (343.4) | | Porosity | % (%) | 0 | (0) | | Color | — | tan | — | | Flexural Strength | MPa (lb/in2x103) | 400-620 | (58-90) | | Elastic Modulus | GPa (lb/in2x106) | 200 | (29) | | Shear Modulus | GPa (lb/in2x106) | — | — | | Bulk Modulus | GPa (lb/in2x106) | — | — | | Poisson’s Ratio | — | — | — | | Compressive Strength | MPa (lb/in2x103) | 1800-4820 | (270-700) | | Hardness | Kg/mm2 | 1100 | — | | Fracture Toughness KIC | MPa•m1/2 | 6-10 | — | Maximum Use Temperature
(no load) | °C (°F) | 400-980 | (4750-1800) | | Thermal | | | | | Thermal Conductivity | W/m•°K (BTU•in/ft2•hr•°F) | 2 | (13.9) | | Coefficient of Thermal Expansion | 10–6/°C (10–6/°F) | 5–10 | (2.8–5.5) | | Specific Heat | J/Kg•°K (Btu/lb•°F) | 418 | (0.1) | | Electrical | | | | | Dielectric Strength | ac-kv/mm (volts/mil) | 2–10 | (50–250) | | Dielectric Constant | — | — | — | | Dissipation Factor | — | — | — | | Loss Tangent | — | — | — | | Volume Resistivity | ohm•cm | >1010 | — | *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. Back to top Standard Products | Custom Products and Services | Case Studies | Materials
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