Zirconia Toughened Alumina (ZTA)

Zirconia Toughened Alumina, (ZTA) is often used in wear applications as an intermediate solution between alumina and zirconia

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> Zirconia Increases Strength

The main advantage of Zirconia Toughened Alumina (ZTA) is the additional strength and toughness over alumina with a lower cost than zirconia (YTZP, MSZ, CSZ).

The combination of aluminum oxide and 10-20% zirconium oxide provides a much higher strength, toughness, hardness and wear resistance than alumina alone.

The 20-30% increase in strength often provides the design criteria needed at a much lower cost than using zirconia.

A process called transformation toughening is the phenomenon that increases the fracture toughness of ZTA. When placed under stress, the zirconia particles change their crystal structure from a tetragonal to a monoclinic structure, causing a volume expansion that compresses the surrounding crack in the alumina matrix.

ZTA should be considered for any application where structural strength is needed that exceeds the standard alumina properties.

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Prime Features
Higher strength than alumina Lower cost than zirconia
High corrosion resistance High erosion resistance
High fracture toughness Capable of a very fine surface finish
Typical Applications
Standoffs Pump piston sleeves
Insulators Instrument
Probe bodies Sensor bulbs
Pump components Valve seals
Bushings Impellers
Fluid delivery system components Analytical instrument columns
Application Limitations
ZTA does provide a higher strength than alumina but the temperature limitation of 1500 C (2732 F) must be observed. Above this temperature the strength contribution of the zirconia is reduced. Use in moist environments at temperatures above 250C also must be carefully considered as the zirconia is subject to low temperature degradation.
Materials Property Chart
  Zirconias
  Property ASTM Method Units ZTA-02 US Patent 8679995 ZTA-14 ZTA-20
General Crystal Size (Average) Thin Section Microns <2 6 3
Color -- -- Off White White White
Gas Permeability -- atms-cc/sec gas tight <10-10 gas tight <10-10 gas tight <10-10
Water Absorption C 20-97 % 0 0 0
Mechanical Density C 20-97 g/cc 3.96 4.17 4.30
Hardness Vickers 500gm GPa (kg/mm2) 14 (1440) 14.5 (1478) 14.4 (1470)
Hardness -- R45N 81 82 82
Fracture Toughness Notched Beam MPam1/2 5 6 6
Flexural Strength (MOR)
(3 point) @ RT
F417-87 MPa (psi x 103 448 (65) 586 (85) 620 (90)
Tensile Strength @ RT -- MPa (psi x 103) 259 (38) 344 (50) 350 (51)
Compressive Strength @ RT -- MPa (psi x 103) 2413 (350) 2758 (400) 2758 (400)
Elastic Modulus C848 GPa (psi x 106) 358 (52) 338 (49) 338 (49)
Poisson's Ratio C848 -- 0.23 0.23 0.23
Thermal C.T.E. 25 - 100° C C 372-96 x 10-6/C 6.7 6.0 6.0
C.T.E. 25 - 300° C C 372-96 x 10-6/C 8.1 7.0 7.0
C.T.E. 25 - 600° C C 372-96 x 10-6/C 8.3 7.1 7.1
Thermal Conductivity @ RT C 408 W/m K 27 24 24
Max Use Temp -- Farenheit (°F) 2732 2730 2730
-- Celsius (°C) 1500 1500 1500
Electrical Dielectric Strength (.125" Thick) D 149-97A V/mil 230 250 250
Dielectric Constant @ 1 MHz D 150-98 -- 10.5 12.5 12.5
Dielectric Constant D 2520-95 -- -- -- 12.4
@ Gigahertz D 2520-95 -- -- -- 9.4
Dielectric Loss @ 1 MHz D 150-98 -- 0.0003 0.0006 0.0006
Dielectric Loss D 2520-95 -- -- 0.0005 0.0005
@ Gigahertz D 2520-95 -- -- 9.4 9.4
Volume Resistivity, 25°C D 257 ohms-cm > 1 x 1014 > 1 x 1014 > 1 x 1014
Volume Resistivity, 300°C D 1829 ohms-cm 3 x 1012 1 x 1010 1 x 1010
Volume Resistivity, 500°C D 1829 ohms-cm 6 x 1010 2 x 109 2 x 109
Volume Resistivity, 700°C D 1829 ohms-cm 6 x 109 2 x 108 4 x 108
Note: The information in this data sheet is for design guidance only. STC does not warrant this data as absolute values. Forming methods and specific geometry could affect properties. Slight adjustments can be made to some of the properties to accommodate specific customer requirements. Most of the dense materials in the table are resistant to mechanical erosion and chemical attack. STC has performed ASTM testing qualification for certain compositions, in accordance with ASTM D2442. Please consult our technical staff for appropriate material and specific test results.