Effects of Calcium Oxide and Magnesium Oxide Stabilizing Agents on the Critical Transformation Size of Tetragonal Zirconia

2020 ◽  
Vol 980 ◽  
pp. 15-24
Author(s):  
Liang Zhao ◽  
Shuang Yao ◽  
Yong Qiang Li ◽  
Zhi Long Zhao ◽  
Qun Hu Xue
Keyword(s):  
Particle Size ◽  
Magnesium Oxide ◽  
Calcium Oxide ◽  
Tetragonal Phase ◽  
Room Temperature ◽  
Tetragonal Zirconia ◽  
Phase Content ◽  
Stabilized Zirconia ◽  
Stabilizing Agents ◽  
Zirconia Nanopowders

The preparation of tetragonal zirconia nanopowders by sol–gel method using zirconium oxychloride as raw material, ammonia water and sodium hydroxide solution as precipitant, and calcium oxide or magnesium oxide powders as stabilizing agents is described. After suction filtration, drying, and calcination, tetragonal zirconia nanopowders with different particle size and tetragonal phase content were obtained. The particle size and phase composition of the powders are characterized by using a laser particle size analyzer and an X-ray diffractometer, and the tetragonal phase content and grain size are calculated from the crystal plane formula and Scherrer formula. The analysis of the relationship between the tetragonal phase content and the particle size of the zirconia nanopowders stabilized by calcium oxide and magnesium oxide at room temperature reveals the inhibitory effect of the stabilizing agents on the growth of zirconia grains. The stabilized zirconia nanopowder is finer than unstabilized zirconia nanopowder, and the particle distribution is more uniform in the former. The stabilizing effect of calcium oxide is superior to that of magnesium oxide; the critical transformation size of the zirconia grains stabilized by calcium oxide is the largest, and that of unstabilized zirconia is the smallest. The critical transformation size of calcium oxide-stabilized, magnesium oxide-stabilized, and unstabilized zirconia nanopowders is 18–22.6 nm, 24–28 nm, and 26–33.6 nm, respectively. Under the same calcination condition, the calcium oxide-stabilized zirconia nanopowder retains the highest tetragonal phase content at room temperature.

scholarly journals Equimolar Yttria-Stabilized Zirconia and Samaria-Doped Ceria Solid Solutions

Ceramics ◽  
2018 ◽  
Vol 1 (2) ◽  
pp. 343-352 ◽  
Author(s):  
Reginaldo Muccillo ◽  
Daniel de Florio ◽  
Eliana Muccillo
Keyword(s):  
Tetragonal Phase ◽  
Room Temperature ◽  
Single Phase ◽  
Rietveld Analysis ◽  
X Ray Diffraction ◽  
Ceramic Powders ◽  
Stabilized Zirconia ◽  
X Ray ◽  
Ceria Solid Solutions ◽  
Attrition Milling

Compositions of (ZrO2)0.92(Y2O3)0.08 (zirconia: 8 mol % yttria—8YSZ) and (CeO2)0.8(Sm2O3)0.2 (ceria: 20 mol % samaria—SDC20) ceramic powders were prepared by attrition milling to form an equimolar powder mixture, followed by uniaxial and isostatic pressing. The pellets were quenched to room temperature from 1200 °C, 1300 °C, 1400 °C and 1500 °C to freeze the defects configuration attained at those temperatures. X-ray diffraction analyses, performed in all quenched pellets, show the evolution of the two (8YSZ and SDC20) cubic fluorite structural phases to a single phase at 1500 °C, identified by Rietveld analysis as a tetragonal phase. Impedance spectroscopy analyses were carried out in pellets either quenched or slowly cooled from 1500 °C. Heating the quenched pellets to 1000 °C decreases the electrical resistivity while it increases in the slowly cooled pellets; the decrease is ascribed to annealing of defects created by lattice micro-tensions during quenching while the increase to partial destabilization of the tetragonal phase.

scholarly journals Low-temperature degradation resistance and plastic deformation of ATZ ceramics stabilized by CaO

2021 ◽  
Vol 2103 (1) ◽  
pp. 012075
Author(s):  
AA Dmitrievskiy ◽  
DG Zhigacheva ◽  
VM Vasyukov ◽  
PN Ovchinnikov
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Plastic Deformation ◽  
Compressive Strength ◽  
Phase Composition ◽  
Low Temperature ◽  
Uniaxial Compression ◽  
Calcium Oxide ◽  
Tetragonal Phase ◽  
Room Temperature

Abstract In this work, the phase composition (relative fractions of monoclinic m-ZrO2, tetragonal t-ZrO2, and cubic c-ZrO2 phases) and mechanical properties (hardness, fracture toughness, compressive strength) of alumina toughened zirconia (ATZ) ceramics, with an addition of silica were investigated. Calcium oxide was used as a stabilizer for the zirconia tetragonal phase. It was shown that CaO-ATZ+SiO2 ceramics demonstrate increased resistance to low-temperature degradation. The plasticity signs at room temperature were found due to the SiO2 addition to CaO-ATZ ceramics. A yield plateau appears in the uniaxial compression diagram at 5 mol. % SiO2 concentration. It is hypothesized that discovered plasticity is due to the increased t→m transformability.

Phase instability in ZrO2–NiAl functionally graded materials

1997 ◽  
Vol 12 (10) ◽  
pp. 2589-2593 ◽  
Author(s):  
Yi-Rong He ◽  
Vidya Subramanian ◽  
John J. Lannutti
Keyword(s):  
Residual Stress ◽  
Functionally Graded Materials ◽  
Tetragonal Phase ◽  
Room Temperature ◽  
Functionally Graded ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Graded Materials ◽  
Temperature Transformation ◽  
Phase Retention

Sedimentation in organic solvents was followed by hot-pressing to produce 2 mole % yttria stabilized zirconia-NiAl functionally graded materials (FGM's). These FGM's were better able to accommodate high levels of residual stress than alumina-NiAl FGM's; this is possibly due to enhanced tetragonal phase retention. However, we found that the zirconia layer in these FGM's subsequently experiences room temperature transformation of t-ZrO2 to m-ZrO2.

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.

Thermal-Spray Yttria-Stabilized Zirconia Phase Changes During Annealing

2000 ◽  
Author(s):  
J. Ilavsky ◽  
J. Wallace ◽  
J.K. Stalick
Keyword(s):  
Tetragonal Phase ◽  
Monoclinic Phase ◽  
Tetragonal Zirconia ◽  
Rietveld Analysis ◽  
Phase Changes ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Yttria Partially Stabilized Zirconia ◽  
Zirconia Phase ◽  
Plasma Sprayed

Abstract Phase stability of the thermal barrier deposits made from yttria-partially-stabilized zirconia (Y-PSZ) is a requirement for extended service lifetime. The response of Y-PSZ plasma-sprayed deposits to annealing at 1000 °C, 1200 °C, and 1400 °C with times from 1 to 1000 hours has been evaluated using Rietveld analysis of neutron diffraction data. Results show that yttria concentration of the as-sprayed tetragonal zirconia component generally decreased with increasing annealing temperature and time. As the yttria content in the tetragonal phase approached a limiting concentration, the tetragonal phase transformed into monoclinic phase on cooling. An increase in monoclinic phase content was clearly observable after annealing 24 hours at 1400 °C and was nearly 35 % after 100 hours at 1400 °C. A similar trend was observed at 1200 °C for longer annealing times, with monoclinic phase formation beginning after 400 hours. At 1000 °C experimental times were not sufficient for monoclinic phase to form although a decrease in the yttria concentration in the tetragonal phase was observed. Keywords: neutron scattering, yttria-stabilized zirconia, phase composition, Rietveld analysis

Influence of atmosphere on crystallization of zirconia from a zirconium alkoxide

1998 ◽  
Vol 13 (5) ◽  
pp. 1230-1237 ◽  
Author(s):  
David E. Collins ◽  
Keith J. Bowman
Keyword(s):  
Tetragonal Phase ◽  
Transformation Temperature ◽  
Polymorphic Transformation ◽  
Room Temperature ◽  
Oxygen Vacancies ◽  
Metastable Phase ◽  
Tetragonal Zirconia ◽  
Monoclinic Symmetry ◽  
Processing Times ◽  
Zirconium Alkoxide

Dibutoxybis (acetylacetonato) zirconium, a difunctional zirconium alkoxide, was polymerized at 130 °C for 5 h in vacuo to produce oligomers that could be pyrolyzed to form a tetragonal zirconia (t-ZrO2), metastable at room temperature. This metastable phase was retained considerably below the equilibrium transformation temperature (∼1200 °C) without the use of dopants. Comparative pyrolysis of the oligomers between 600 and 900 °C in either flowing O2 or N2 for processing times under 12 h indicated t-ZrO2 nucleated first. Pyrolysis in oxygen facilitated transformation to the monoclinic symmetry, whereas pyrolysis in nitrogen demonstrated retention of the tetragonal phase. The formation of oxygen vacancies during pyrolysis, their role in stabilizing the metastable tetragonal phase, and contributions of O2 and crystallite size in the polymorphic transformation are discussed.

Ferroelectric Tunability Studies in Doped BaTiO3 and Ba1−xSrxTiO3

2000 ◽  
Vol 658 ◽  
Author(s):  
Dong Li ◽  
M. A. Subramanian
Keyword(s):  
Curie Temperature ◽  
Phase Change ◽  
Tetragonal Phase ◽  
Cryogenic Temperature ◽  
Room Temperature ◽  
Co Doping ◽  
Structure Changes

ABSTRACTAcceptor and Donor codoped BaTiO3 and Ba1−xSrxTiO3 are prepared. For Ba1−xLaxTi1−xFexO3,BaTiO3 remains as tetragonal phase up to about 5mol% LaFeO3. For x ≥0.06, the structure changes to cubic at room temperature. The phase change shifts the Curie temperature to lower value and increases the tunability at room temperature. Doping of other acceptor (Al, Cr) and donor (Sm, Gd, Dy) ions has the same effect although with varying levels of tuning. BaTiO3: 4%LaFeO3 has the highest tunability among the studied systems, which is even higher than Ba0.6Sr0.4TiO3. Co-doping of (La, Fe) and (La, Al) in Ba1−xSrxTiO3 also lowers the Curie temperature and increases the tunability of high Ba content samples at cryogenic temperature.

scholarly journals Effect of Al2O3 Sandblasting Particle Size on the Surface Topography and Residual Compressive Stresses of Three Different Dental Zirconia Grades

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 610
Author(s):  
Hee-Kyung Kim ◽  
Byungmin Ahn
Keyword(s):  
Particle Size ◽  
Residual Stresses ◽  
Surface Topography ◽  
Tetragonal Zirconia ◽  
Peak Shift ◽  
Confocal Laser ◽  
Compressive Stresses ◽  
Surface Topographies ◽  
Altered Surface ◽  
Tetragonal Zirconia Polycrystal

This study investigated the effect of sandblasting particle size on the surface topography and compressive stresses of conventional zirconia (3 mol% yttria-stabilized tetragonal zirconia polycrystal; 3Y-TZP) and two highly translucent zirconia (4 or 5 mol% partially stabilized zirconia; 4Y-PSZ or 5Y-PSZ). Plate-shaped zirconia specimens (14.0 × 14.0 × 1.0 mm3, n = 60 for each grade) were sandblasted using different Al2O3 sizes (25, 50, 90, 110, and 125 μm) under 0.2 MPa for 10 s/cm2 at a 10 mm distance and a 90° angle. The surface topography was characterized using a 3-D confocal laser microscopy and inspected with a scanning electron microscope. To assess residual stresses, the tetragonal peak shift at 147 cm−1 was traced using micro-Raman spectroscopy. Al2O3 sandblasting altered surface topographies (p < 0.05), although highly translucent zirconia showed more pronounced changes compared to conventional zirconia. 5Y-PSZ abraded with 110 μm sand showed the highest Sa value (0.76 ± 0.12 μm). Larger particle induced more compressive stresses for 3Y-TZP (p < 0.05), while only 25 μm sand induced residual stresses for 5Y-PSZ. Al2O3 sandblasting with 110 μm sand for 3Y-TZP, 90 μm sand for 4Y-PSZ, and 25 μm sand for 5Y-PSZ were considered as the recommended blasting conditions.

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