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About Zirconia , ZrO2 material

Zirconia, ZrO2 exists as a monoclinic crystal at room temperature inverting to tetragonal phase above approximately 1200. The addition of large amounts of a stabilizer such as magnesium oxide will induce a cubic crystal structure during firing that does not revert to the monoclinic phase upon cooling. The addition of generally less than 10% by weight of stabilizers yields high-density ceramic bodies know as transformation toughened zirconia. Two fundamentally different microstructures exist depending upon the added stabilizer.





The addition of MgO yield a relatively coarse grained (50-100 micron) microstructure known as Mg-PSZ.

The grains are predominantly cubic morphology with a fine precipitate of tetragonal phase dispersed within the grain.

 
   
Yttria, Y2O3, additions yield an extremely fine grained (less than I micron) microstructure known as

Y-PSZ or TZP or tetragonal zirconia polycstal. The individual grains are completely tetragonal.

The transformation toughened zirconias are characterized by high strength and fracture toughness approaching that of the cemented carbides. The characteristics result from stress induced phase transformations of the tetragonal crystals to the monoclinic phase with a corresponding change in volume and local stress field. The TZPís show superior strength and toughness; however, their properties suffer at high temperatures, thus limiting their use to applications below 500. The Mg-PSZís retain their desirable properties at temperatures approaching 1100.

ZrO2 is available in a wide variety of shapes and sizes and amenable to a wide variety of cold and hot forming techniques.

Zirconia is stable in oxidizing and mildly reducing atmospheres. It reacts with carbon, nitrogen and hydrogen at temperatures above 2200. It is inert to acids and bases at room temperature with the exception of HF and does not react with the refectory metals up to 1400. However, the capability is strongly dependent upon the type and quantity of stabilizer used in the ceramic.

Major developing markets for Mg-PSZ, Y-PSZ or TZP include thermal barriers for high efficiency heat engines, cutting tools, wear parts, biological implants, certain ferrous metallurgical applications and high temperature oxygen sensors.

Advanced ZrO2 Ceramics for Structural Applications:

K-Style provides two basic grades of Mg-PSZ and one grade of Y-TZP.

Mg-PSZ:

MS GRADE: Superior fracture toughness and high mechanical strength.average thermal shock resistance. Best suited applications bellow 800 and minimum thermal cycling.

TS GRADE: Excellent thermal shock resistance, slightly lower strength than MS grade, but higher toughness. Best suited for high temperature (above 600) applications or thermal cycling.

Y-TZP GRADE: Superior mechanical Strength and high toughness, slightly lower thermal shock resistance than MG-PSZ. Best suited for application below 500.


The Standard Specification of the Materials:

  PROPERTIES

Mg-PSZ MS-GRADE

Mg-PSZ TS GRADE

Y-TZP
  Chemistry

10molMgO+ZrO2

10molMgO+ZrO2

3molY2O3+ZrO2

  Crystal Morphology

Cubic,tetragonal,
monoclinic

Cubic,tetragonal,
monoclinic

Tetragonal

  Density(g/cm3) 20C

5.74

5.73

6.03

  Flexural Strength 20C
  4Poin Bend (MPa) 820C

820
450

720
370

800-1200
300

  Compressive 20C
  Strength (Mpa) 800C

1990
1500

1900
1750

2000
1100

  Fracture Toughness KIC 20C
  (Mpa m1/2 ) 800C

8-12
5

10-15
5

6-8
3-4

  Weibull Modulus (m) 20C

30

30

15

  Poissons Ratio 20C

0.13

0.13

0.28

  Hardness (HV) 20C

1120

1020

1200

  Coefficient of Sliding Friction

0.15

0.15

0.15

  Thermal conductivity (W/mK)

3.08

3.05

2.7

  Specific Heat (J/g/k) 0.45 0.45 0.45
  Thermal Shock Resistance
  Down-Shock
  Up-Shock Residual Strength
375C 500C 170C
  Coefficient of Expansion
  X 106/C 20C-100C
10.2 10.2 9.6
  Maximum Use Temperature () 800 1100 500

In addition to the three grades mentioned above, when appropriator, we have the ability to "Customize" 
our materials to better suit specific requirements.

 
  © 1995~2006 K-Style Advanced Ceramics Co., Ltd.      info@ZrO2.com-                    Top of the page