Analytical TEM study of a yttria stabilized zirconia/glass composite

1988 ◽  
Vol 46 ◽  
pp. 572-573
Author(s):  
Yung-Jen Lin ◽  
Peter Angelini ◽  
Martha L. Mecartney
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Room Temperature ◽  
Tetragonal Zirconia ◽  
Yttria Stabilized Zirconia ◽  
Boundary Phase ◽  
Stabilized Zirconia ◽  
High Toughness ◽  
M Phase

Yttria stabilized zirconia is a versatile ceramic material. It can be used for structural components or as a solid electrolyte. Its properties (such as high toughness) are strongly affected by the microstructure. In partially stabilized zirconia, the high toughness is mainly due to the toughening effect of a tetragonal (t) to monoclinic (m) phase transformation in the vicinity of a crack. Retention of tetragonal zirconia at room temperature is important for fabricating transformation toughened materials. To completely retain tetragonal zirconia at room temperature the grain size of the material must be less than a critical size. In yttria stabilized zirconia this critical grain size depends on the yttria concentration. Grain growth of yttria stabilized zirconia is also influenced by the amount of yttria in the grains. These previous studies, however, have focused on the behavior of materials with minimal glassy grain boundary phases. In contrast, in commercial polycrystalline zirconia often a significant amount of glassy grain boundary phase is present. This current research seeks to elucidate the effects of these grain boundary phases on the grain growth in yttria stabilized zirconia ceramics.

Elaboration of Sol-Gel Derived Hydroxyapatite / Yttria Stabilized Zirconia Composite Coatings Obtained for Biomedical Application

2011 ◽  
Vol 312-315 ◽  
pp. 894-899
Author(s):  
Sahar Salehi ◽  
Mohammad Hosseien Fathi
Keyword(s):  
Grain Size ◽  
Crystallite Size ◽  
Grain Growth ◽  
Biomedical Application ◽  
Composite Coatings ◽  
Sol Gel ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Nanostructured Composite

In this study, nanostructured composite coatings of hydroxyapatite (HA)/ 30wt% yttria stabilized zirconia (YSZ) coatings containing 0, 3, 5, and 8 mol% Y2O3 (namely; HA-0YSZ, HA-3YSZ, HA-5YSZ, and HA-8YSZ) were successfully synthesized using the sol-gel method. The crystallite size of the coating was about ~44-58 nm for tetragonal and cubic zirconia grain size and 75-87 nm for hydroxyapatite grain size. Crack-free and homogeneous HA-YSZ composite coatings were obtained with no observable defects. The uniform distribution of zirconia particles in a composite would be highly beneficial for obtaining homogeneous coatings of HA-YSZ film and would hinder grain growth of HA phase during calcinations. In vitro evaluation in 0.9% NaCl showed that Ca2+ dissolution rate of composite coatings was lower than pure HA coatings.

scholarly journals Grain Boundary Resistivity of Yttria-Stabilized Zirconia at 1400°C

2013 ◽  
Vol 2013 ◽  
pp. 1-4 ◽  
Author(s):  
J. Wang ◽  
A. Du ◽  
Di Yang ◽  
R. Raj ◽  
H. Conrad
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Electric Field ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Brick Layer Model ◽  
Dc Electric Field ◽  
Lower Temperature ◽  
Boundary Width ◽  
Grain Boundary Resistivity

The grain size dependence of the bulk resistivity of 3 mol% yttria-stabilized zirconia at 1400°C was determined from the effect of a dc electric field Ea=18.1 V/cm on grain growth and the corresponding electric current during isothermal annealing tests. Employing the brick layer model, the present annealing test results were in accordance with extrapolations of the values obtained at lower temperature employing impedance spectroscopy and 4-point-probe dc. The combined values give that the magnitude of the grain boundary resistivity ρb=133 ohm-cm. The electric field across the grain boundary width was 28–43 times the applied field for the grain size and current ranges in the present annealing test.

Effect of CoO Doping on the Sintering Ability and Mechanical Properties of Y-TZP

2004 ◽  
Vol 449-452 ◽  
pp. 265-268 ◽  
Author(s):  
Tetsuhiko Onda ◽  
H. Yamauchi ◽  
Motozo Hayakawa
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Refinement ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Tetragonal Zirconia ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Boundary Strength

The effect of CoO addition into Y-TZP (Yttria doped Tetragonal Zirconia Polycrystals) was studied on the evolution of its sintering ability, grain size, grain boundary structure and mechanical properties. The doping of a small amount of CoO effectively reduced the sintering temperature. A small amount of CoO up to ~ 0.3 mol% was effective for the suppression of grain growth, but the addition of 1.0 mole % resulted in an enhanced grain growth. The hardness and toughness of the CoO doped TZP were about the same as those of undoped TZP. Furthermore, despite the grain refinement, CoO doped TZP did not exhibit improved mechanical properties. This may be suggesting that CoO dopant had weakened the grain boundary strength.

Chemically Derived Yttria-Stabilized Zirconia for Plasma-Spraying

1990 ◽  
Vol 180 ◽  
Author(s):  
Fawzy G. Sherif ◽  
H. Herman
Keyword(s):  
Grain Size ◽  
Tetragonal Zirconia ◽  
Yttria Stabilized Zirconia ◽  
Metal Alkoxides ◽  
Stabilized Zirconia ◽  
Spray Coatings ◽  
Plasma Spray Coatings ◽  
Hydrolysis Conditions ◽  
Controlled Hydrolysis ◽  
Zirconia Powders

ABSTRACTYttria-stabilized zirconia powders were prepared by three chemical routes utilizing emulsion hydrolysis techniques. Metal alkoxides, acetates and mixtures of alkoxides and acetates were used as starting materials. Under controlled hydrolysis conditions, particles with different morphology and size were obtained. Spherical or granular particles in the range of 20–60u in diameter were formed. The grain size varied from 0.1–0.2u. The powders were applied successfully as plasma spray coatings. The chemical uniformity was demonstrated by the presence of 100% non-transformable tetragonal zirconia in the powder and in the coating.

The Grain Size Effect on the Yttria Stabilized Zirconia Grain Boundary Conductivity

2010 ◽  
Vol 10 (11) ◽  
pp. 7411-7415 ◽  
Author(s):  
Victor Ivanov ◽  
Sergey Shkerin ◽  
Alexey Rempel ◽  
Vladimir Khrustov ◽  
Alexander Lipilin ◽  
...  
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Size Effect ◽  
Yttria Stabilized Zirconia ◽  
Grain Size Effect ◽  
Stabilized Zirconia ◽  
Boundary Conductivity

The Effect of Heat-Treatment on Thermal Conductivity of Silicon Nitride Ceramics

2011 ◽  
Vol 484 ◽  
pp. 52-56
Author(s):  
Katsumi Yoshida ◽  
Yuki Sekimoto ◽  
Keiichi Katayama ◽  
Thanakorn Wasanapiarnpong ◽  
Masamitsu Imai ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Heat Treatment ◽  
Grain Size ◽  
Grain Boundary ◽  
Grain Growth ◽  
Glassy Phase ◽  
Boundary Phase ◽  
Sintering Additives ◽  
Heat Treated ◽  
Si3n4 Ceramics

Alpha- or beta-Si3N4 powder with larger grain size was uses as starting material, and the effect of heat-treatment on thermal conductivity of Si3N4 ceramics using MgO, Y2O3 and SiO2 as sintering additives was investigated in terms of their microstructure and the amount of grain boundary phase. Most of the components derived from sintering additives existed as glassy phase in sintered Si3N4. After heat-treatment at 1950oC for 8 h, the amount of glassy phase significantly decreased, and then small amount of glassy phase existed in Si3N4 ceramics was crystallized as Y2O3 and Y2Si3N4O3. In the case of Si3N4 ceramics using SN-7 powder, thermal conductivity of heat-treated Si3N4 was around twice of the value of sintered Si3N4, and the thermal conductivity was increased from 41.4 to 87.2 W/m•K due to not only the reduction of grain boundary phase but also the grain growth. In the case of Si3N4 using SN-F1 powder, thermal conductivity of Si3N4 ceramics was also significantly increased from 36.0 to 73.2 W/m•K after heat-treatment. In this case, the reduction of grain boundary phase mainly affected the thermal conductivity of Si3N4 ceramics because the grain size of heat-treated Si3N4 was nearly the same as that of sintered Si3N4. The reduction of grain boundary phase from Si3N4 was effective for the improvement of their thermal conductivity in addition to grain growth of Si3N4.

Grain size of MgO and polymorphic phases of ZrO2 in zirconia-toughened MgO

1993 ◽  
Vol 8 (11) ◽  
pp. 2757-2760 ◽  
Author(s):  
Yasuro Ikuma ◽  
Toshio Sugiyama ◽  
Junko Okano
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Cooling Rate ◽  
Grain Growth ◽  
Room Temperature ◽  
Boundary Limit ◽  
Transmission Electron ◽  
Electron Microscopes

Zirconia-toughened MgO was manufactured and examined by scanning and transmission electron microscopes. It was found that ZrO2 particles that are present on the MgO grain boundary limit the grain growth of MgO. The cooling rate has an effect on the ZrO2 phase in zirconia-toughened MgO fired in a cubic ZrO2–MgO field, but it does not have an effect on the ZrO2 phase in specimens fired in a tetragonal ZrO2–MgO field. Tetragonal ZrO2 was retained at room temperature in zirconia-toughened MgO.

Precursor scavenging of the resistive grain-boundary phase in 8 mol% yttria-stabilized zirconia: Effect of trace concentrations of SiO2

2001 ◽  
Vol 16 (8) ◽  
pp. 2377-2383 ◽  
Author(s):  
Jong-Heun Lee ◽  
Toshiyuki Mori ◽  
Ji-Guang Li ◽  
Takayasu Ikegami ◽  
John Drennan ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Yttria Stabilized Zirconia ◽  
Impurity Level ◽  
Boundary Phase ◽  
Inhomogeneous Distribution ◽  
Stabilized Zirconia ◽  
Boundary Area ◽  
Average Grain Size ◽  
Trace Concentrations ◽  
Boundary Conduction

The influence that trace concentrations of SiO2have on improving grain-boundary conduction via precursor scavenging using additional heat treatment at 1200 °C for 40 h before sintering was investigated. At a SiO2-impurity level (SIL) ≤160 ppm by weight, the grain-boundary resistivity (ρgb) decreased to 20% of its value, while no improvement in grain-boundary conduction was found at a SIL ≥ 310 ppm. The correlation between the resistance per unit grain-boundary area, rgb, and average grain size indicated that the inhomogeneous distribution of the siliceous phase in the sample with a SIL ≥ 310 ppm hampered the scavenging reaction.

A Comparative Study of Superplastic Deformation and Cavitation Failure in a Yttria Stabilized Zirconia and a Zirconia Alumina Composite

1990 ◽  
Vol 196 ◽  
Author(s):  
A. H. Chokshi ◽  
D. J. Schissler ◽  
T.-G. Nieh ◽  
J. Wadsworth
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Superplastic Deformation ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Experimental Conditions ◽  
Fine Grained ◽  
Grain Sizes ◽  
Alumina Composite ◽  
Cavitation Failure

ABSTRACTA fine grained yttria stabilized zirconia and a zirconia composite containing 20% alumina exhibit superplastic characteristics, with optimum elongations to failure of ≥500%. There is microstructural evidence for deformation enhanced grain growth and concurrent cavitation in both of these superplastic ceramics. Grain sizes after superplastic deformation may be several times larger than the initial grain size, and the level of cavitation can attain values as high as ≥30% under some experimental conditions. This report presents in a comparative format some recent experimental results on the microstructural aspects of superplastic deformation and concurrent cavitation in these superplastic ceramics.

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