Impedance spectroscopy of Mg-partially stabilized zirconia and cubic phase decomposition

Partially stabilized zirconia (PSZ) materials were fabricated using 4 wt% CaO, 3 wt% MgO, and 5.4 wt% Y2O3 as stabilizing agents together with monoclinic zirconia powder. The physical properties, phase compositions, and microstructures of the Ca-PSZ, Mg-PSZ, and Y-PSZ samples were investigated by X-ray diffraction, scanning electron microscopy, and energy spectrum analysis. A crucible method was used to explore the relationship between the stabilizing agent and erosion resistance to alkaline steel slag. The results revealed that the zirconia materials stabilized by different stabilizing agents showed obvious differences in their bulk densities, apparent porosities, microstructures, and erosion resistances to alkaline steel slag. The structure of Y-PSZ showed highest density, containing a small number of uniformly distributed pores. In terms of Mg-PSZ, the intergranular bonding in its structure was observed to not be close, and the sample contained some cracks, but no pores. A large number of intragranular pores and a small number of overall pores was observed in Ca-PSZ, resulting in this material having the lowest bulk density. The pores and cracks provide the path to penetrate and diffuse for alkaline steel slag, which weakens the corrosion resistance of PSZ materials. The phase composition of the affected layers in all of the samples after corrosion was almost completely transformed from monoclinic phase to cubic phase, and the phase transition of both the original and transition layers was not obvious due to the formation of a slag film. Y-PSZ did not react with components of the steel slag such as SiO2 and Al2O3, showing the best corrosion resistance to alkaline steel slag.

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Microstructural Investigations of Plasma Sprayed Yttria Partially Stabilized Zirconia TBC: in Relation to Thermomechanical Resistance and High Temperature Oxidation Mechanisms

Volume 5: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education ◽

10.1115/92-gt-317 ◽

1992 ◽

Cited By ~ 2

Author(s):

S. Alperine ◽

L. Lelait

Keyword(s):

High Temperature ◽

Chemical Reduction ◽

Diffusion Mechanism ◽

Cubic Phase ◽

High Temperature Annealing ◽

Stabilized Zirconia ◽

Temperature Oxidation ◽

Partially Stabilized Zirconia ◽

Yttria Partially Stabilized Zirconia ◽

Plasma Sprayed

This study deals with microstructural investigations of plasma sprayed yttria partially stabilized zirconia thermal barrier coatings, performed by classical and analytical transmission electron microscopy. The aim of the study was to determine eventual relationships between coating microstructure and toughness. The ceramic/metal interface which plays an important role during TBC thermomechanical sollicitation, has also been studied. In the 6 to 8 weight % Y2O3 range, the metastable tetragonal t’ phase is observed, showing special faulted microstructural features, such as grain twinning and antiphase boundary planes. Moreover, after high temperature annealing in air, a very fine and stable precipitation of the equilibrium cubic phase appears. It is believed that these microstructural elements could act as crack deviation sites and enhance coatings intrinsic toughness. Microstructural investigations of the alumina scales grown during high temperature annealing reveal yttrium segregation at oxide grain boundaries as well as significant quantities of zirconium inside the alumina grains. The oxide growth seems to be dominated by a classical grain boundary oxygen diffusion mechanism. The presence of zirconium inside the alumina grains suggests that Al2O3 also partially forms by chemical reduction of ZrO2 by Al.

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Microstructural Investigations of Plasma-Sprayed Yttria Partially Stabilized Zirconia TBC (In Relation to Thermomechanical Resistance and High-Temperature Oxidation Mechanisms)

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.2906802 ◽

1994 ◽

Vol 116 (1) ◽

pp. 258-265 ◽

Cited By ~ 16

Author(s):

S. Alpe´rine ◽

L. Lelait

Keyword(s):

High Temperature ◽

Chemical Reduction ◽

Diffusion Mechanism ◽

Cubic Phase ◽

High Temperature Annealing ◽

Stabilized Zirconia ◽

Temperature Oxidation ◽

Partially Stabilized Zirconia ◽

Yttria Partially Stabilized Zirconia ◽

Plasma Sprayed

This study deals with microstructural investigations of plasma-sprayed yttria partially stabilized zirconia thermal barrier coatings, performed by classical and analytical transmission electron microscopy. The aim of the study was to determine eventual relationships between coating microstructure and toughness. The ceramic/metal interface, which plays an important role during TBC thermomechanical solicitation, has also been studied. In the 6–8 wt. percent Y2O3 range, the metastable tetragonal t′ phase is observed, showing special faulted microstructural features, such as grain twinning and antiphase boundary planes. Moreover, after high-temperature annealing in air, a very fine and stable precipitation of the equilibrium cubic phase appears. It is believed that these microstructural elements could act as crack deviation sites and enhance the coatings’ intrinsic toughness. Microstructural investigations of the alumina scales grown during high-temperature annealing reveal yttrium segregation at oxide grain boundaries as well as significant quantities of zirconium inside the alumina grains. The oxide growth seems to be dominated by a classical grain boundary oxygen diffusion mechanism. The presence of zirconium inside the alumina grains suggests that Al2O3 also partially forms by chemical reduction of ZrO2 by Al.

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Investigation of Scandia Stabilized Zirconia(ScSZ) - Yttria Stabilized Zirconia(YSZ) Composite Electrolyte for Intermediate Temperature Fuel Cells

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.124-126.795 ◽

2007 ◽

Vol 124-126 ◽

pp. 795-798 ◽

Cited By ~ 1

Author(s):

Hui Jeong Son ◽

Tak Hyoung Lim ◽

Dong Ryul Shin ◽

Rak Hyun Song ◽

Sung Hyun Kim

Keyword(s):

Electrical Conductivity ◽

Impedance Spectroscopy ◽

Milling Process ◽

Yttria Stabilized Zirconia ◽

Cubic Phase ◽

Wet Milling ◽

Stabilized Zirconia ◽

Composite Electrolyte ◽

Long Term Stability

The effect of ScSZ - YSZ composite on stabilization and electrical conductivity has been investigated. Composite of (8YSZ)x(10ScSZ)(1-x)(x=0~1) were mixed by wet milling process and sintered at 1400°C for 5h and characterized by XRD, SEM, dilatometry and impedance spectroscopy. the long-term stability of the electrolyte materials was examined at 900°C for up to 1000h. The cubic phase shifts from an YSZ character to a ScSZ character with increase in percentage of ScSZ. The conductivity of composite with increasing ScSZ content is slightly higher than YSZ. Especially, above 50wt% ScSZ composition exhibited higher electrical conductivity. All compositions showed conductivity degradation after annealing at 900°C for 1000h.

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