Zirconia (ZrO2) offers three advantages over alumina: it is more refractory, having a melting point some 500oC above alumina. It is readily machined and gives a high quality surface finish and is a useful oxygen anion conductor for use in sensors and fuel cells. However, it is considerably more expensive than alumina.

Zirconia 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.

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.

PropertyUnitTestZirconia Toughened AluminaPartially Stabilised ZirconiaFully Stabilised Zirconia
Densityg.cc-1ASTM C204.05.76.0
Elastic ModulusGPaASTM C848360200200
Flexural StrengthMPaASTM F417450620900
Compressive StrengthMPaASTM C773290017502500
Fracture Toughness RangeMPaNOTCHED BEAM5-61113
HardnessGPaROCKWELL 45N857783
Thermal ConductivityW/mKASTM C20272.22.2
CTE 25-10010(-6)/0C/ASTM C3728.210.110.3
Thermal Shockdelta TcNOTE3300350350
Dielectric Strengthac-kv/mm (6.25mm)ASTM D1169.09.49.4
Dielectric Loss250C@1MHzASTM D25200.00050.0010.001
Volume Resistivity1000C ohm-cmASTM D182910^6<10^2<10^1
  • 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. The change in temperature where a sharp decrease in flexural strength is observed is listed as ‘delta Tc’.
  • CHEMICAL RESISTANCE – Although all alumina and zirconia ceramics are highly resistant to chemical attack, it is recommended that specific applications are discussed with Almath Crucibles to ensure optimum ceramic selection.

View our full range of Zirconia products.

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