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Fig. 1 The flow chart of 3Y-TZP powder prepared by the gel solid-state method.
Thermogravimetry and differential thermal analysis(TG–DTA) were carried out on the dried
gelcasts obtained using a thermal analyzer (Netzsch STA 429C). The gelcasts sintered for 2 h at
different temperatures were characterized by X-ray diffraction (XRD). The particle size of the powder
after srirring-milling was measured by the Laser Particle Analyzer (Master sizer-2000,
Malvern).Microstructure characterization of all specimens was carried out on a Hitachi X-650
scanning electronic microscope (SEM). Bulk density of the ceramics was measured by the
Archimedes method. Rectangular bars for bending strength tests (3 mm×4 mm in cross section and 36
mm long) were cut, and three-point bending strength measurements were carried out with an inner
span of 30 mm and a crosshead speed of 0.5mm/s at room temperature using an Instron-l195
Universal Test Machine. Vickers hardness and fracture toughness, KIC, were determined using an
indentation technique with a Vicker indenter.
Results and Discussion
Gel solid-state method was used free radical polymerization of polymer monomer to form the
polymer network structure. Ceramic raw materials were distributed evenly and restricted among this
three-dimensional netword. In the subsequent drying and calcining process, the raw material powder
did't deposited, thus facilitating the homogeneous reaction of powders.
TG–DTA was used in analysing the thermal decomposition of the gelcasts. The two endothermic
reactions in Fig. 2, peaking at 106°C and at 220°C, with a corresponding loss of mass in the TG curve,
are due to removal of adsorbed water and coordination in the inner sphere; In the temperature 249°C,
there is a mass loss for the specimen accompanied by a large exothermic DTA peak, this attributes to
the de-esterification of the polymeric resin. The other exothermic process occurring from 350°C to
400°C is associated with the full decomposition of the organic polymer.
AM
MBAM Dispersant, Water
NH3⋅H2O
ZrO2
Y(NO3)3·6H2O
Drying gel
Powder
Ceramic slurry
Wet gel
Mixing Milling
Catalyst Initiator
Drying
Calcining
62 Chinese Ceramics Communications II
Fig. 3 shows the results of XRD measurements in 3Y-TZP powders calcined at different
temperatures for 2 h. the phases of powder is monoclinic zirconia in 900°C. tetragonal zirconia peak
was appeared in 1150°C and its intensity was increased with the rising of temperature.
Fig. 2 TG–DTA curves of the gelcasts. Fig. 3 XRD patterns of the powder sintered at
different temperatures.
Table 1 Mechanical properties of 3Y-TZP ceramics sintered at 1410°C and 1520°C.
Sintering temperature 1410°C 1520°C
Bulk density (g⋅cm-3
) 5.98 6.03
Vickers hardness (kg/mm2) 1211 1250
Fracture toughness (MPam1/2
) 7.89 9.03
Bending strength (MPa) 567 812
Fig. 4 SEM image of the powder calcined in 1300°C for 2h.
SEM image of the 3Y-TZP powders calcined in 1300°C for 2h and stirring-milled is shown in Fig.
4. It can be seen that the particle is well-crystallized with average grain size of 230 nm; and the
particles are slightly agglomerated. The results were consistent with the value tested by Laser Particle
Analyzer.
Table 1 shows the mechanical properties of 3Y-TZP ceramics sintered at 1410°C and 1520°C.
Vickers hardness, fracture toughness and bending strength of ceramics increased with increasing
sintering temperatures.
SEM photographs of the fracture surfaces of 3Y-TZP ceramics sintered at 1410°C (Fig. 5a) and
1520°C (Fig. 5b) for 2h are shown in Fig. 5. Fig. 5a reveals a basically dense microstructure, but the
grains do not grow fully. The ceramics is dense and the grains have grown fully with an estimated
Advanced Materials Research Vol. 412 63
average size 0.4µm. The results were agreement with the mechanical properties of 3Y-TZP ceramics
above. The microstructure of grain determined the high mechanical properties of ceramics. The
average size and degree of growth were important for the mechanical properties, especially the
bending strength.
Fig. 5 SEM photographs of the fracture surfaces of ceramics sintered at (a) 1410°C and (b) 1520°C.
Summary
The 3Y-TZP powder synthesized by gel solid-state method had very good properties. Characteristics
of the ceramics sintered by this powder as below: Bulk density was 6.03 g⋅cm-3
, Vickers hardness
was1250 kg/mm2, Fracture toughness was 9.03 MPam
1/2 and Bending strength was 812 Mpa. So it
was a promising method and easily used in industrial production.
Acknowledgements
The authors would like to thank the National Science Foundation of China (60807036) and the
Leading Foundation of Shanghai (08JC1417200) for supporting the research.
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64 Chinese Ceramics Communications II
Chinese Ceramics Communications II 10.4028/www.scientific.net/AMR.412 Synthesis and Characterization of 3Y-TZP by Gel Solid-State Method 10.4028/www.scientific.net/AMR.412.61
DOI References
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