Influence of grain boundary β-spodumene glass on the superplastic flow in tetragonal zirconia polycrystal (TZP)

1995 ◽  
Vol 202 (1-2) ◽  
pp. 249-255 ◽  
Author(s):  
P. Thavoriniti ◽  
T. Sakuma
Keyword(s):  
Grain Boundary ◽  
Tetragonal Zirconia ◽  
Superplastic Flow ◽  
Tetragonal Zirconia Polycrystal

Grain-Boundary Structure and Phase-Transformation Mechanism in Yttria-Stabilized Tetragonal Zirconia Polycrystal

2007 ◽  
Vol 558-559 ◽  
pp. 921-926
Author(s):  
Koji Matsui ◽  
Hidehiro Yoshida ◽  
Yuichi Ikuhara
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Phase Transformation ◽  
Grain Boundary ◽  
Grain Growth ◽  
Tetragonal Zirconia ◽  
Cubic Phase ◽  
Phase Boundaries ◽  
Transmission Electron ◽  
Tetragonal Zirconia Polycrystal

The microstructures in 3 mol% Y2O3-stabilized tetragonal zirconia polycrystal (Y-TZP) sintered at 1100°-1650°C were investigated to clarify cubic-formation and grain-growth mechanisms. The cubic phase in Y-TZP appeared at 1300°C and its mass fraction increased with increasing sintering temperature. High-resolution transmission electron microscopy (HRTEM) and nanoprobe X-ray energy dispersive spectroscopy (EDS) measurements revealed that no amorphous layer existed along the grain-boundary faces in Y-TZP, and Y3+ ions segregated not only along the tetragonal-tetragonal phase boundaries but also along tetragonal-cubic phase boundaries. Scanning transmission electron microscopy (STEM) and nanoprobe EDS measurements revealed that the Y3+ ion distribution was nearly homogeneous up to 1300°C, but cubic phase regions with high Y3+ ion concentration clearly formed inside grains at 1500°C. These results indicate that cubic phase regions are formed from the grain boundaries and/or the multiple junctions in which Y3+ ions segregated. We termed such a new diffusive transformation phenomenon “grain boundary segregation-induced phase transformation (GBSIPT)”. The grain-growth mechanism is controlled by the solute-drag effect of Y3+ ions segregating along the grain boundary.

Effect of Grain Boundary Segregated Dopant on Phase Stability in Tetragonal Zirconia Polycrystal

2010 ◽  
Vol 654-656 ◽  
pp. 2208-2211
Author(s):  
Yorinobu Takigawa ◽  
Takahisa Yamamoto ◽  
Kenji Higashi
Keyword(s):  
Grain Size ◽  
Phase Transformation ◽  
Grain Boundary ◽  
Phase Stability ◽  
Boundary Diffusion ◽  
Tetragonal Zirconia ◽  
Transformation Behavior ◽  
Hydroxyl Ion ◽  
Boundary Stress ◽  
Tetragonal Zirconia Polycrystal

The effect of grain boundary segregated dopant on phase stability of tetragonal zirconia polycrystal (TZP) is examined by accelerated exposure tests ageing in hot water. The materials used in this study are 3 mol%Y2O3 stabilized TZP (3Y-TZP) and 0.1mol%SiO2-doped 3Y-TZP. Accelerated exposure tests in an autoclave reveal that the tetragonal phase stability of 3Y-TZP in water is highly affected by the grain boundary segregated dopant and the grain size. When the grain size of TZP is about 0.55μm, the change in phase transformation behavior with dopant is explained from the change in grain boundary diffusivity of hydroxyl ion. Grain boundary diffusion of hydroxyl ion must be blocked by the presence of some segregated ion which reduces the effective area of grain boundary diffusion. On the other hand, when the grain size is about 0.35μm, the phase transformation behavior seems to be controlled by the grain boundary stress. Decreased grain boundary stress by the segregation of some dopant must enhance the phase transformation of 3Y-TZP.

Microstructures after Bending Deformations to Fracture of Zr Ion Irradiated Superplastic Ceramic 3Y-TZP

2007 ◽  
Vol 551-552 ◽  
pp. 475-480
Author(s):  
Takaaki Sakuma ◽  
Yoshinobu Motohashi ◽  
Taiju Shibata ◽  
Kazuhiro Sawa ◽  
Masahiro Ishihara
Keyword(s):  
Mechanical Properties ◽  
Grain Boundary ◽  
Intergranular Fracture ◽  
Ion Irradiation ◽  
Tetragonal Zirconia ◽  
Surface Region ◽  
Tandem Accelerator ◽  
Tetragonal Zirconia Polycrystal

The effects of Zr ion irradiation on the mechanical properties of a typical superplastic ceramic, 3mol% yttria stabilized tetragonal zirconia polycrystal (3Y-TZP), were examined and discussed. The specimens were irradiated by Zr11+ ions with 130MeV at fluence level of 3.5×1012 and 2.1×1013 ions/cm2 in the TANDEM accelerator at Tokai Reasearch Establishment of JAEA. Microstructures after annealing and bending deformations to fracture of Zr ion irradiated 3Y-TZP were examined. It was found that the ratio of intergranular fracture to intragranular fracture was increased in the region that was affected by Zr ion irradiation. It seemed that grain boundary cohesion became relatively weak in the irradiated surface region. The influence of Zr ion irradiation on the mechanical properties almost disappeared when the irradiated 3Y-TZP was subsequently heated to 1173K.

Space-charge concepts on grain boundary impedance of a high-purity yttria-stabilized tetragonal zirconia polycrystal

2001 ◽  
Vol 16 (9) ◽  
pp. 2739-2751 ◽  
Author(s):  
Jong-Sook Lee ◽  
Doh-Yeon Kim
Keyword(s):  
Grain Boundary ◽  
Space Charge ◽  
High Purity ◽  
Tetragonal Zirconia ◽  
Impedance Analysis ◽  
Dopant Profile ◽  
Brick Layer Model ◽  
Temperature Equilibrium ◽  
Boundary Impedance ◽  
Tetragonal Zirconia Polycrystal

A detailed impedance analysis using the brick-layer model is performed on a high-purity yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Space-charge impedance is generally formulated and expressions for the respective space-charge models are therefrom derived depending on whether dopant ions are mobile or immobile. Pronounced yttrium segregation in Y-TZP is also considered in the analysis in that the dopant profile is assumed to be frozen from a high-temperature equilibrium distribution. Comparison with experimental observations shows that the electrically measured grain-boundary thickness corresponds to the Schottky-barrier width, slightly modified by the dopant segregation. The grain-boundary resistance is not consistent with any space-charge models and the strong defect interaction due to the yttrium enrichment is suggested to be mainly responsible.

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