MEL Products for Ceramic Applications

The use of zirconium oxides in technical ceramics is well established, notably for their electrical, wear and heat resistant properties. Our doped and undoped zirconium oxides are vital ingredients in a huge range of industrial and domestic products.

SPECIAL CERAMIC GRADES

In order to achieve the required ceramic properties, most zirconia ceramic bodies require the presence of cubic / tetragonal phases in their microstructure. This can be achieved by the mixing of certain metal oxides with monoclinic grades of zirconia prior to pressing and firing. This gives rise to products having low shrinkage and high fired densities.

The SC series of zirconium oxides has been designed for use where a high level of control of physical and chemical properties is required. S, SC30 and SC15 are all monoclinic at normal temperatures. Reversible inversion to the tetragonal form takes place at about 1000°C, in the absence of other components. Stabilisation of the SC grades is possible with Y₂O₃, CeO₂, MgO or CaO and when used in the production of Partially Stabilised Zirconia Ceramics, give high strength, high density products.

Areas of application include high performance engineering ceramics and oxygen sensors. The chemical route employed in their manufacture ensures that all the SC grades are of high purity. Selection of individual grades will depend on the particle size distribution, chemical purity and surface area required for a given application.

Please refer to our Product List for further details of our Special Ceramic Grades

GLASS AND HIGH PURITY GRADES

Zirconium oxide is an important constituent of certain special optical and ophthalmic glasses, and is the basic raw material used in the manufacture of high purity ceramics. Whether the zirconium oxide is a minor component in a glass batch or a major constituent in a gemstone melt, the chemical purity and consistency are of paramount importance.

G grade oxides have controlled chemical compositions, with for example, iron oxide at levels of 60 ppm (G60), or 5 ppm (GL). Zirconium oxide and other oxides of group IVB metals are all colourless; indeed, one of the advantages of zirconium oxide is its exceptionally low absorption in the visible and near UV wavebands. With the exception of Group IVB metals, all transition metals are typically present at less than 5 ppm.

At room temperature, the G grade oxides are monoclinic, but reversible inversion to the tetragonal phase takes place at about 1000°C in the absence of other components. In ophthalmic and other optical glasses, the presence of zirconium oxide enables high refractive indices to be achieved without the loss of durability. Zr is also the basis of a range of non-oxide glasses for use in optical fibres and other high technology applications.

Please refer to our Product List for details of our Glass and Gemstone Grades.

ELECTRONIC GRADES

Many electronic components contain zirconium oxide. The E grade series of zirconium oxides has been designed to meet the raw material specifications of the electronic industry. These grades are all of high purity, with controlled physical properties.

At normal temperatures the crystal phase is monoclinic, but reversible inversion to the tetragonal phase takes place at about 1000°C, in the absence of other components. If zirconium oxide is part of a lead zirconate titanate formulation, for example, the high reactivity of the E grade zirconium oxides optimizes zirconate phase formation, and results in products with consistent electronic properties and minimum rejects.

For dielectrics such as the barium titanates, and for many piezoelectric ceramics, E30, E20 and E15 grades normally suffice. Where a highly reactive zirconia is required, E101 grade, with high surface area and exceptionally low silica level, is recommended.

Please refer to our Product List for further details or our Electronic Grades

YTTRIA DOPED SPECIAL CERAMIC GRADES

MEL Chemicals have developed a range of yttria doped zirconium oxides for users who are not equipped for the in-situ stabilisation of our monoclinic grades. The powders are for use in applications such as engineering ceramics, milling media, fiber optic ferrules, oxygen sensors and solid oxide fuel cells. The properties of these grades of oxide make them suitable for tape casting, injection moulding and iso-static pressing techniques.

MELox Grades for Structural Ceramics

• These are new products specifically designed to be sinter active, of high purity and consistency.
• Manufactured using a chemical processing route, these powders have a homogeneous yttria distribution.
• Supplied as spray dried granules for improved handling characteristics.
• Grades available with or without binder.
• M.O.R. >1000MPa.

MELox Grades for Other Applications

• Ceramics manufactured from our powders are white in colour.
• The crystallite size can be easily controlled.
• The grain size of the powders are low, typically, 0.1 to 1 µm.
• The powders can be sintered at 1450-1500°C.
• The chemical route used to manufacture the powders results in a homogeneous stabiliser distribution.
• The versatility of the process allows a rapid response to the demands which may be placed on the powders.

Please refer to our Product List for further details of our Yttria Doped Special Ceramic Grades.

MAGNESIA DOPED SPECIAL CERAMIC GRADES

MEL Chemicals have developed magnesia doped zirconium oxides for users who are not equipped for in-situ stabilisation of our monoclinic grades. The materials are for use as engineering and structural ceramics and exhibit excellent thermal shock resistance. Grades are available with or without binder.

Please refer to our Product List for further details of our Magnesia Doped Special Ceramic Grades.

CERAMIC PIGMENT GRADES

Grades are available for all zircon and zirconia pigments. S grade can be used for zircon-iron pinks, zircon-vanadium blues, zircon-praseodymium yellow and zirconia vanadium yellows/oranges. MS2 has been designed to be used where shade variations for some colours are required.

Please refer to our Product List for further details of our Ceramic Pigment Grades.

NANOSTRUCTURED CERAMICS

Why nanostructured ceramics?

• Potentially higher electric conductivity (ionic conductors)
• Potentially higher hardness and strength (engineering ceramics)
• Reduction in sintering temperatures, therefore saving energy

MEL zirconia nano suspensions can be concentrated:

• Low viscosity nano suspensions with solids contents up to 75 wt%.
•  Retention of the desirable nano primary particle size.
• Enhancing their suitability for fabrication into ceramics by methods such as slip casting and ink jet printing.

Formation of green bodies:

• Homogeneous, high density green bodies without agglomeration.

Retention of nanostructure during densification:

• Full density without significant grain growth.
• Microstructures exhibit zero porosity and an average grain size <80 nm.
• Lower sintering temperature required.

Please refer to our Product List for further details of our Nano Materials

Below are images showing the fracture surface of green (slip cast) samples from a 58 wt% suspension and a fired ceramic with a density >99% of theoretical. The average grain size in the fired ceramic is ~80 nm.