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Zirconia
Zirconia
Zirconia Crucibles (ZrO2) offer three advantages over their alumina crucible counterparts: they are more refractory, having a melting point some 500oC above alumina. They are readily machined and give a high quality surface finish and are a useful oxygen anion conductor for use in sensors and fuel cells. However, they are considerably more expensive than alumina.
Zirconium dioxide has the complication of being metastable and needs to be stabilised before it can be put to use. The addition of small quantities of stabilising oxides such as CaO, MgO and best of all Y2O3 allow the high temperature cubic phase to stabilise itself. Partially stabilised zirconia can also be used as a toughening agent in alumina.
Zirconia-toughened alumina (ZTA) shows a considerable improvement in strength and more importantly toughness. As a result, these ceramics can be used in areas of extreme mechanical abrasion and thermal shock.
Fully stabilised zirconia (FSZ) produces a high-density ceramic on sintering. The grain size is relatively large at 10-40m m and the ceramics are often translucent in appearance. Recent optimisation of zirconia powders have resulted in a readily sinterable high purity product.
Salient Features:
- High temperature range
- Very High Mechanical Strength
- Excellent wear and abrasion resistance
- High Impact Resistance and Toughness
- Usable for many cycles at a high life time
- Very Low Thermal Conductivity
- Highly resistant to most acids
- Suitable for precious metals and alloys (except palladium)
- Inert material
- Wide range of geometries and dimensions possible
Other Information about Zirconia
Zirconia is not suitable for use in inductive heating and has a low thermal shock resistance. Slow heating and slow cooling is advisable. Slow ramp rate and cooling rate are highly recommended to minimize the thermal shock on crucibles. When increasing the temperature, special attention should be paid on two sensitive temperature periods: not exceeding 3°C/MIN during 100°C —300°C and 1050°C -1200°C. The rate can be faster in other temperature ranges, but it is recommended to be less than 5°C /MIN.
To take the crucible directly out of furnace at high temperature may cause crack. if possible, take it out when the temperature is under 100°C.
Zirconia crucibles should not be heated by torch or furnaces that cannot control temperature change rate. The uneven heating can cause crack.
Zerconia Applications
Zirconium Oxide Crucibles deliver cleaner melts at temperatures up to 1900°C and beyond. They are engineered for the melting of superalloys and precious metals and deliver heat-up and cool-down schedules that keep your foundry productive. They are widely used in:
- Chemical calcining
- Metal casting
- Metal melting, especially in superalloy and precious metals industries
- Thermal analysis crucibles
Typical zirconia labware include:
- Crucible
- Boat
- Tray
- Tube
- Rod
- Mortar & Pestle
- Jar
- Balls
- Custom Zirconia
MATERIAL PROPERTIES
Please note that the information set forth herein is offered for comparison only, and is not to be construed as absolute engineering data or constituting a warranty or representation for which we assume legal responsibility.
Composition
| Oxide | Percentage |
|---|---|
| ZrO2 | 95.3 |
| MgO | 2.2 |
| SiO2 | 1.2 |
| Al2O3 | 0.7 |
| CaO | 0.2 |
| Fe2O3 | 0.2 |
| TiO2 | 0.2 |
| PROPERTY | TEST | UNITS | S-YTZ |
|---|---|---|---|
| Colour | Pure White | ||
| Density | ASTM-C20 | g/cc | 6.02 |
| Average Crystal Size | THIN-SECTION | Microns | 1 |
| Water Absorption | ASTM-373 | % | 0 |
| Gas Permeability | 0 | ||
| Flexural Strength (20°C) | ASTM-F417 | MPa (psi x 103) | 1240 (180) |
| Elastic Modulus (20°C) | ASTM-C848 | GPa (psi x 103) | 310 (30) |
| Poission’s Ratio (20°C) | ASTM-C848 | 0.23 | |
| Compressive Strength (20°C) | ASTM-C773 | MPa (psi x 103) | 2500 (363) |
| Hardness | KNOOP 1000 gm ROCKWELL 45 N |
GPa (kg x mm2) R45 N |
12.7 (130) 81 |
| Tensile Strength (25°C) | ACMA TEST #4 | MPa (psi x 103) | 550 (79) |
| Fracture Toughness KIC | NOTCHED BEAM | MPa m½ | 13 |
| Thermal Conductivity (20°C) | ASTM-C408 | W/mK | 2.2 |
| Coefficient of Thermal Expansion (25-1000°C) |
ASTM-C372 | 1X10-6/°C | 10.3 |
| Specific 100°C | ASTM-E1269 | J/Kg K | 400 |
| Thermal Shock Resistance TC | °C | 350 | |
| Dielelectric Strength | ASTM-D116 | Ac-kV/mm (ac V/mil) | 9 (228) |
| Dielctric Constant (1 MHz) | ASTM-D150 | 29 | |
| Dielectric Loss (1 MHz) | ASTM-D150 | 0.001 | |
| Volume Resistivity 25°C 500°C 1000°C |
ASTM-D1829 | Ohm-cm | >1013 2.0 X 104 < 103 |
DATA MEASUREMENTS – All data measurements are typical and made at room temperature unless otherwise noted.
THERMAL SHOCK RESISTANCE – Tests are run by quenching samples into water from various elevated temperatures. Zirconia crucibles are sensitive to thermal shock. Try to warm up the furnace chamber slowly. So that the crucibles can be evenly heated to reduce the impact of thermal shock.
CHEMICAL RESISTANCE – Although all zirconia ceramics are highly resistant to chemical attack, it is recommended that specific applications are discussed with us to ensure optimum ceramic selection.
Note:- The above information is believed to be correct but does not purport to be all inclusive and shall be used only as a guide. The information in this document is based on the present state of our knowledge and is applicable to the product with regard to appropriate safety precautions. It does not represent any guarantee of the properties of the product. Venture Scientific® shall not be held liable for any damage resulting from handling or from contact with the above product.