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Advanced Zirconia Materials

Unlike other ceramic materials, zirconium oxide (ZrO2 –also known as zirconia) is a material with very high resistance to crack propagation. Zirconium oxide ceramics also have very high thermal expansion and are therefore often the material of choice for joining ceramic and steel.TopTek has continuously been developping new materials for specialized applications. Below, you'll find the our latest offerings including in which features a class-leading endurance limit. Please contact TopTek for more information.

Worth knowing:

Properties of Zirconium Oxide (ZrO2)

  • High thermal expansion (α=11 x 10-6/K, similar to some types of steel)

  • Excellent thermal insulation/low thermal conductivity
    (2.5 to 3 W/mK)

  • Very high resistance to crack propagation,high fracture toughness (6.5 to 8 MPam1/2)

  • Ability to conduct oxygen ions(used for the measurement of oxygen partial pressures in lambda probes)

Aluminiumoxid Gefügebild

Aluminiumoxid Gefügebild

Partially Stabilized Zirconia Materials
Background
Zirconia (ZrO2) is an excellent engineering ceramic due to its desirable physical properties such as extremely high melting temperature, high strength and fracture toughness with optimum wear resistance,which is an advantage for several dental and orthopedic application. However the phase changes that it undergoes during sintering are deleterious to these properties and hence pure zirconia is not a useful engineering material.

Zirconia Phase Transformations

At room temperature, zirconia exists on the monoclinic phase. When heated to about 1170°C, it undergoes a phase transformation from monoclinic to tetragonal and a volume shrinkage of more than 3-5%. Further heating produces another change to cubic at 2370°C. The cubic phase is maintained until the melting point or zirconia is reached 2680°C.
The large volumetric change associated with this phase transformation is a large enough to affect the structural integrity of the material. Repeated heating and cooling cycles would result in further erosion of mechanical integrity and properties
.

Producing Stabilized and Partially Stabilized Zirconia
The additions of cubic oxides such as MgO, CaO, Y2O3, CeO2 and other rare earth oxides stabilize the high temperature cubic phase all the way back to room temperature. They also tend to decrease the transformation temperature.

Transformation Toughening in Partially Stabilized Zirconias
If produced properly, the resultant microstructure consists of lens or elliptical-shaped precipitates of tetragonal zirconia within the cubic grains. Normally the tetragonal phase would transform into the monoclinic phase at low enough temperatures, but the high strength of the cubic phase prevents the required expansion from happening, freezingin the tetragonal precipitates. Monoclinic zirconia may also be present in the cubic grains and at the grain boundaries.

Applications of Partially Stabilized Zirconias
Dies and tooling
Knives, scissors and blades
Wear resistant components including bearings and linings
Pump parts
Grinding media

Applications of Partially Stabilized Zirconias
Dies and tooling
Knives, scissors and blades
Wear resistant components including bearings and linings
Pump parts
Grinding media


Y-TZP Zirconia
Yttrium oxide is used as the stabiliser. This material is predominantly tetragonal in structure. Y-TZP has the highest flexural strength of all the zirconia based materials, particularly when HIPed. The fine grain size of Y-TZP lends itself to be used in cutting tools where a very sharp edge can be achieved and maintained due to its high wear resistance.
The fine grade size leads to a very dense, non porous ceramic with excellent mechanical strength, corrosion resistance, impact toughness, thermal shock resistance and very low thermal conductivity. Due to its characteristics Y-TZP is used in wear parts, cutting tools and thermal barrier coatings.

Key Features
Excellent mechanical strength
Excellent wear resistance
High impact resistance
Very low conductivity

Main Applications
Structural ceramics
Wear parts
Thermal barrier coating
Dental ceramics
Fiber optic
Ferrules and sleeves
Grinding media
Oxygen sensors

Ce-TZP Zirconia
Cerium Oxide is used as the stabilizer and it is possible to produce the most dense zirconia ceramic of 6.2 g/cm3. Due to the materials good wear resistance and high density it is used for producing milling media, particular for milling highly viscous compounds and paints.. The higher density also allows for the production of smaller grinding media leading to higher grinding efficiency and reduced grinding times.
The wear resistance, fracture toughness and mechanical strength is similar to Y-TZP.

Main Applications:
Milling media
Structural ceramics
Automotive catalyticsystems


Key features:

High density
Excellent wear resistance
High impact resistance
Good fracturetoughness


Mg-PSZ Zirconia
Magnesium oxide is used as the stabiliser. This cubic phase material is loaded with tiny tetragonal phase precipitates, giving a very high level of transformation toughness. Mg-PSZ is able to give the highest level of fracture toughness.
It has excellent mechanical properties, includ
ing high strength, fracture toughness, wear resistance, good thermal shock and low thermal conductivity.
Due to these characteristics it finds use in high wear and corrosion applications including valves, pumps and liners. It is the material of choice for the chemical processing and petrochemical industries


Key fe
atures:
Excellent fracture toughness
Excellent wear resistance
Corrosion resistant
Good thermal shock resistance


Main Applications:
Pump parts
Valve components
Bearings
Bearings







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