Yttria-stabilized ZrO2 Research Articles

Robust, lightweight, thermally-insulating felt assembled by hollow and continuous yttria-stabilized ZrO2 fibers

Advanced hollow ceramic fiber materials with excellent thermal insulation and lightweight characteristics are urgently needed in rapidly developing areas such as aerospace. However, creating such hollow ceramic fiber materials has proven to be extremely challenging for current synthetic techniques. Here, we introduce a facile approach for the production of hollow yttria-stabilized zirconia (YSZ) fiber felts through sol–gel solution centrifugal spinning. It is found that the hollow structure can be effectively controlled by adjusting the mass ratios of inorganic salts and PVP, as well as the calcination temperatures. The resulting hollow YSZ felts exhibit low density (38 mg cm−3), robust tensile strength (439.56 ± 24.23 kPa), significant stretchability (>10 %), exceptional oxidation and high-temperature resistance, refractory properties, and outstanding thermal insulation characteristics (0.019 W/m K−1 at room temperature and 0.103 W/m K−1 at 1000℃). The successful synthesis of such fascinating materials may provide new insights into the design and development of hollow ceramic fibers.

Fabrication and Characterization of CeO2-Doped Yttria-Stabilized ZrO2 Composite Particles

Fabrication and Characterization of CeO2-Doped Yttria-Stabilized ZrO2 Composite Particles

Computational discovery of fast interstitial oxygen conductors.

New highly oxygen-active materials may enhance many energy-related technologies by enabling efficient oxygen-ion transport at lower temperatures, for example, below ~400 °C. Interstitial oxygen conductors have the potential to realize such performance but have received far less attention than vacancy-mediated conductors. Here we combine physically motivated structure and property descriptors, ab initio simulations and experiments to demonstrate an approach to discover new fast interstitial oxygen conductors. Multiple new families were found, which adopt completely different structures from known oxygen conductors. From these families, we synthesized and studied oxygen kinetics in La4Mn5Si4O22+δ, a representative member of the perrierite/chevkinite family. We found that La4Mn5Si4O22+δ has higher oxygen-ion conductivity than the widely used yttria-stabilized ZrO2, and among the highest surface oxygen exchange rates at the intermediate temperature of known materials. The fast oxygen kinetics is the result of simultaneously active interstitial and interstitialcy diffusion pathways. We propose that the essential features for forming an effective interstitial oxygen conductor are the availability of electrons and structural flexibility, enabling a sufficient accessible volume. This work provides a powerful approach for understanding and discovering new interstitial oxygen conductors.

Assessment of geometrical variability in 3D printed ZrO2: Effects of printing and thermal post-processing

3D printing is developing rapidly and enables the production of parts manufactured using different materials. These includes zirconium dioxide (ZrO2), which can be of particular interest for bone tissue engineering and implantology. However, highly accurate part-dimensions are a must for these applications, which is why this study addresses geometrical deviations which occur during the printing process and thermal post-processing.Six sets of test geometries with 50 individual features were 3D printed with two different ZrO2 slurries (3 mol% yttria-stabilized ZrO2) and scanned with a profilometer. After debinding and sintering, the profilometer scan was repeated and the deviations and shrinkage factors were determined.A notable difference is observed when the same ceramic is processed using two different slurries. For instance, one used ceramic slurry, LithaCon 210, exhibits shrinkage factors of shrXY=21.2±3.4%(n=78) and shrZ=23.6±0.54%(n=24) for protruding structures, while the other ceramic slurry, LithaCon 280, shows shrinkage factors of shrXY=21.7±3.3%(n=78) and shrZ=24.5±0.55%(n=24).Geometric deviations differed for intruding (like holes and slots) and protruding (like pillars) geometries, being more pronounced in case of intruding geometries, especially where printing overhangs occur.Although the shrinkage during sintering needs further investigation, these experimental findings are a good starting point to validate and refine simulation models for shrinkage and improve production processes of 3D printed ceramics.

Vat photopolymerization 3D printing of yttria-stabilized ZrO2 ceramics: effects of a sintering additive (Na2O – 2SiO2), biocompatibility, and osteointegration

Effects of a liquid-phase sodium disilicate additive on the properties of ZrO2 ceramics containing 3 mol.% of Y2O3 and 2 wt% of Al2O3 are presented, including phase composition, microstructure, shrinkage, porosity, and bending strength. The distribution of elements along grain boundaries and the composition in a selected area of a lamella were investigated by transmission electron microscopy in pure and additive-containing samples. As a result of the introduction of the additive, sintering activity of the material increased, and the sintering temperature diminished down to 1150 °C. Thus, dense nanocrystalline materials with a crystallite size of 50–70 nm and a bending strength of up to 450 MPa were obtained. Optimized polymer-ceramic suspensions were used to produce objects with complex geometric shapes by 3D molding technology through layer-by-layer vat polymerization. According to in vitro assays, the obtained samples are nontoxic and cytocompatible with human osteosarcoma MG-63 cells, and according to in vivo experiments, are biocompatible and showing osseointegrative properties when implanted into the rat tibia.

Limits of critical grain size for the tetragonal phase stabilization in CaO‐doped ZrO2 ceramic and associated benefits

AbstractRecently, CaO‐doped (≤4 mol.%) tetragonal zirconia (CaSZ) ceramic was recommended as a potential alternative to yttria‐stabilized ZrO2 (YSZ). Here, we investigate the limits of starting particle sizes on the stability of tetragonal (t) phase and other associated benefits on measured properties. Synthesized CaSZ powders calcined with different temperatures were used as a mono‐sized or mixed (i.e., two different calcination temperatures) batch fraction for making dense CaSZ ceramic. The mixed‐batch powders were found to be far more efficient in stabilizing the t‐phase in ceramic. Compared to YSZ, CaSZ recorded remarkable enhancement in toughness (up to 8.3 MPa ). Contrary to YSZ, CaSZ ceramic demonstrated outstanding thermal stability.

Achieving Fast Oxygen Reduction on Oxide Electrodes by Creating 3D Multiscale Micro-Nano Structures for Low-Temperature Solid Oxide Fuel Cells.

Fast oxygen reduction reaction (ORR) at the cathode is a key requirement for the realization of low-temperature solid oxide fuel cells (SOFCs). While the design of three-dimensional (3D) structures has emerged as a new and promising approach to improving the electrochemical performance of SOFC cathodes, achieving versatile structures and structural stability is still challenging. In this study, we demonstrate a novel architectural design for a superior cathode with fast ORR activity. By employing a completely new fabrication process comprising a 3D printing technique and pulsed laser deposition (PLD), we design 3D La0.8Sr0.2CoO3-δ (LSC) micro-nano structures with the desired shape. 3D-printed yttria-stabilized ZrO2 (YSZ) microstructures significantly increase the ratio of surface area to volume while maintaining suitable ionic conductivity comparable to that of single-crystalline YSZ substrates. Scanning electron microscopy and energy dispersive X-ray microanalysis reveal the formation of crack- or void-free YSZ microstructures and the uniform deposition of LSC films by PLD on the YSZ microstructures. The 3D LSC micro-nano structures show significantly enhanced oxygen surface exchange coefficients (kchem) extracted from electrical conductivity relaxation (ECR) measurements by up to 3 orders of magnitude relative to the bulk LSC. Furthermore, electrochemical impedance spectroscopy measurements verify the kchem values from ECR and no directional difference in the measured ORR activity depending on the shape of 3D microstructures. The dramatic enhancement of the ORR activity of LSC is attributed to the increased film surface areas resulting from the 3D YSZ microstructures.

Experimental investigation on in-plane compressive behaviour of 2D chiral ceramics

Five kinds of 2D chiral ceramics of 3 mol% yttria-stabilized tetragonal ZrO2 (3Y-TZP) material with an extensive relative density range was fabricated by an additive manufacturing technique based on the digital light processing (DLP) system. The in-plane compressive behaviours of the chiral structures were investigated with a uniaxial compression test. The effects of geometric parameters, including the ligament length-radius ratio and the wall thickness-radius ratio, were studied carefully through experiments. Furthermore, the relationships between Poisson's ratios and relative densities of the five chiral structures were obtained by finite element analysis. The results illustrated that increasing the relative density, like decreasing L/r or increasing t/r, is an excellent way to increase the mechanical properties of chiral ceramics, while decreasing L/r is a better way to increase the energy absorption capacity for chiral ceramics from an engineering perspective. Anti-tetrachiral ceramics own the best energy absorption capacity due to their strong deformation abilities brought by the deformation mode. The Poisson's ratio of 2D chiral structures also varies with the relative density.

High-density monodispersed nickel nanoparticles as highly functional and thermally robust catalysts for solid oxide fuel cells

In this study, we have explored the deposition of highly monodispersed nickel nanoparticles on various supports using a two-step metal–organic precursor thermolysis and reductive annealing process. The process allowed flexible tunability of application-relevant properties, such as nanoparticle size, density and distribution, via the process pressure and deposition cycle control. Ex-situ characterization revealed the presence of carbon in the nanoparticles, necessitating the reductive annealing step to remove residual carbon. The impurities-free nanoparticles were subsequently deposited onto Pr0.5Ba0.5MnO3−δ anodes of solid oxide fuel cells and used to promote the electrochemical oxidation of methane. Impedance spectroscopy of the symmetric cells (Pr0.5Ba0.5MnO3−δ Yttria-stabilized ZrO2 Pr0.5Ba0.5MnO3−δ) revealed a significant enhancement in the catalytic activity of the Ni nanoparticle-coated electrode relative to the bare reference. Moreover, compared to conventional infiltration, the Ni nanoparticles deposited with the strategy outlined in this work showed over a 4-fold improvement in performance with an initial electrode resistance of only 2.1 Ω cm2. This highlights the important role of the deposition method on catalytic performance and the potential of developing highly active electrode materials for direct-hydrocarbon utilization.

Ceramic Foams with Controlled Geometries Through 3D‐Printed Sacrificial Templates

Powder‐based 3D printing was combined with sacrificial templating to realize highly porous yttria‐stabilized ZrO2 (YSZ) ceramic foam objects with well‐defined geometries. The porous sacrificial template is 3D printed using poly(methyl methacrylate) powder. Various methods are evaluated to optimize ceramic slurry infiltration into the 3D‐printed template and subsequent burn‐out. The optimized method yields ceramic foam objects with an open porosity of >66% and replicates the geometry of the 3D‐printed template with high fidelity.

Stability of doped zirconia under extreme conditions: Toward long‐term and secure storage of radioactive waste

AbstractExtreme temperatures and pressures were applied to systems based on stabilized zirconia, ZrO2, doped with Ce4+ ions as surrogate for tetravalent Actinides in order to conclude on their long‐term stability in deep geological underground. Both tetragonal and cubic yttrium‐stabilized ZrO2 (YSZ) exhibit excellent phase and structural stabilities up to 1150 K. In addition, incorporated guest Ce4+ did not show any increase in their mobility at elevated temperatures. Application of external pressure did not induce any structural or phase changes in cubic YSZ doped with 5 at.% Ce as well. However, a corresponding tetragonal analog with lower yttrium content exhibits a second‐order phase transition toward higher cubic symmetry around 9 GPa. Remarkably, no discharge of the guest Ce4+ ions was observed throughout the transition and further upon increase in pressure. This together with T‐dependent data indicates excellent affinity of guest Ce atoms with the host YSZ matrices. The parent YSZ phases are, therefore, promising candidates as host materials for long‐term underground immobilization for radiotoxic tetravalent elements like U, Th, or Pu.

CaO-doped tetragonal ZrO2 nanoparticles as an effective adsorbent for the removal of organic dye waste

In this work, we show the promise and potential of CaO-doped tetragonal ZrO2 nanoparticles as a brilliant adsorbent for toxic azo dye (e.g., Congo red). Contrary to past works, where zirconia has mostly been used as a member to form composite for such adsorption experiments, we show that the system (i.e., doped-ZrO2) alone is capable to portray maximum adsorption capacity up to 186 mg/g for Congo red. High surface area (113 m2/gm) of the synthesized zirconia nanoparticles ensured a rapid removal of the dyes (>85% in just five minutes). The adsorption followed a pseudo-second order kinetic model and fitted closely with the Langmuir isotherm model. Adsorption mechanism reveals the efficacy of the dopant (i.e., CaO) which enabled a chemical interaction (via ion-exchange between the Ca2+ ion of dopant and Na+ ions in the dye molecules) that eventually holds all the success for the adsorption phenomena. To prove the environmental remediation of CaO-ZrO2 as a dye adsorbent in a more practical way, these dye adsorption studies were also carried out in real water. The popular market composition (i.e., yttria-stabilized ZrO2) was also compared and showed modest/little adsorption.

Reversible Martensitic Phase Transition in Yttrium-Stabilized ZrO2 Nanopowders by Adsorption of Water

The present study was aimed at revealing the influence of the mechanical stress induced by water molecule adsorption on the composition of crystalline phases in the ZrO2 + 3 mol% Y2O3-nanoparticles. Three basic methods were used to determine the phase transition: neutron diffraction, Raman microspectroscopic scanning, and X-ray diffraction. The fact of reversible phase-structural β → α transformation and the simultaneous presence of two polymorphic structural modifications (β is the phase of the tetragonal syngony and α of monoclinic syngony in nanosized particles (9 nm)) under normal physical conditions was established by these methods. An assumption was made regarding the connection of the physical mechanism of transformation of the extremely nonequilibrium surface of nanoparticles with electronic exchange of the material of the near-surface layer of nanoparticles with the adsorption layer through donor–acceptor interaction. The principal possibility of creating direct-acting hydroelectric converters based on nanoscale YSZ (Yttria-Stabilized Zirconia) systems due to the reversible character of the considered effect was shown.

Phase stability, thermal shock behavior and CMAS corrosion resistance of Yb2O3-Y2O3 co-stabilized zirconia thermal barrier coatings prepared by atmospheric plasma spraying

Rare-earth element doping has been extensively employed as one of the effective methods to enhance the durability of thermal barrier coatings (TBCs). In present study, ytterbia and yttria co-stabilized zirconia (YbYSZ) coatings and corresponding double-ceramic-layer (DCL) coatings comprised of a dense layer were produced by atmospheric plasma spraying. And the service capability including phase stability, thermal shock behavior and CMAS resistance were systemically evaluated. After heat treatment at 1500 °C for various durations, less monoclinic phase can be found in YbYSZ specimen, indicating excellent phase stability at high temperature. In the thermal shock test, the conventional YbYSZ coatings show a longest thermal shock lifetime, which increases by ~10% as compared with that of conventional yttria-stabilized ZrO 2 (YSZ) coatings. CMAS corrosion resistance of DCL coatings was studied using an isothermal corrosion test at 1300 °C. The results show that YbYSZ systems with a dense layer performed a high resistibility to CMAS corrosion, and less damage can be observed in coatings as well as smaller infiltration depth within the same time. • A double-ceramic-layer (DCL) coating comprised of dense layer was prepared. • The YbYSZ material exhibits higher resistance to high temperature. • The YbYSZ coatings have a longest thermal shock lifetime comparatively. • The DCL-YbYSZ coatings show enhanced CMAS resistance due to high chemical inertness.

Nondestructive Structural Investigation of Yttria-Stabilized Zirconia Fiber Insulation Tile by Synchrotron X-ray In-Line Phase-Contrast Microtomography

Zirconia (ZrO2) aerogels show excellent insulating performance and have been widely applied as a thermal protector in furnaces, nuclear reactors, and spacecraft. The nondestructive determination of their interior microstructure is significant for evaluating their mechanical and insulating performance. In this study, we performed nondestructive structural investigation of an yttria-stabilized ZrO2 fiber insulation tile using synchrotron X-ray in-line phase-contrast microtomography at a pixel resolution of 6.5 µm. Taking advantage of the edge enhancement of phase-contrast imaging, single yttria-stabilized ZrO2 fibers were clearly distinguished; furthermore, interior aggregates were nondestructively observed at this spatial resolution. This work demonstrates the advantages and potential of synchrotron X-ray microtomography for the structural analysis of porous ceramic materials. By combining higher-brilliance synchrotron radiation sources and CCD detectors with higher spatial and temporal resolutions, we anticipate that we can further understand the relationship between aerogel microstructure and function, especially under in-service conditions at high temperatures.

Investigating the Catalytic Requirements of Perovskite Fuel Electrodes Using Ultra-Low Metal Loadings

Solid Oxide Fuel Cells (SOFC) with La0.3Sr0.7TiO3 (LST)–yttria-stabilized ZrO2 (YSZ) anodes were prepared by impregnation of LST into porous YSZ scaffolds and then modified by Atomic Layer Deposition (ALD) of Ni, Pt, Pd, Fe, Co. and CeO2. Weight loadings as low as 0.01% of Pt, Ni, and Pd were sufficient to decrease anode impedances by orders of magnitude for operation in humidified H2 at 973 K. The effects of CeO2, Co, and Fe were less but still significant. Sintering at higher temperatures was important. Possible ways of stabilizing the metal particles and implications for developing ceramic anodes are discussed.

Influence of Surface Adsorption on the Electrical Transport Properties of Ultrathin Indium Tin Oxide Films

We systematically investigated the temperature-dependent behaviors of the resistivities ρ and carrier concentrations n of a series of ultrathin indium tin oxide (ITO) films with thickness t ranging from ∼5.3 to ∼35.0 nm grown on yttrium-stabilized ZrO2 substrates. For the t ≳ 17.5 nm films, the resistivity versus temperature can be described by the Bloch–Grüneisen formula, and the carrier concentration almost retains constant over the whole measured temperature range. For the t ≃ 5.3 nm (7.0 nm) film, the carrier concentration increases with increasing temperature above ∼300 K, and the resistivity initially increases with increasing temperature and then decreases with further increasing temperature above ∼330 K (∼355 K). By comparison of the transport properties of ITO films depositing on different substrates and exposing the films on different atmospheres, it is found that the enhancement of carrier concentration and reduction of resistivity at high temperature regime originate from the dissociative adsorption of water vapor on the surface of the ITO films.

Hot corrosion behavior of ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3 TBCs in CMAS: CaO-MgO-Al2O3-SiO2

Improvement of hot corrosion resistance in calcium-magnesium-aluminosilicate (CMAS: CaO-MgO-Al2O3-SiO2) environments is one of the main goals in the development of aero-engines especially in their thermal barrier coatings (TBCs). In this regard, this study aims to improve the quality and efficiency of the yttria-stabilized ZrO2 (8YSZ) TBCs by substitution of new coatings such as ZGYbY: ZrO2 9.5Y2O3 5.6Yb2O3 5.2Gd2O3. For this purpose, 8YSZ and ZGYbY topcoats with CoNiCrAlY bond coat were applied on IN738LC substrates using atmospheric plasma spray (APS) technique. Hot corrosion behavior of the coatings was investigated in CMAS environment by a furnace method at 1150 °C in the 4-h cycles. Phase and microstructural investigations of the coatings by XRD and FESEM/EDS methods before and after the hot corrosion test indicated the better performance of ZGYbY coating (relative to 8YSZ) in preventing from the diffusion of the CMAS particles. This could be due to the formation of the impermeable apatite compounds (i.e., Ca4Y(Yb/Gd)6O(SiO4)6). Furthermore, the destruction of the TBCs in CMAS environment can be attributed to the diffusion of molten silicates through the pores and micro-cracks of the ceramic top layer to the TBC and then release of the ZrO2 stabilizer and finally the tetragonal to monoclinic ZrO2 phase transformation.

Experimental investigation on bending behaviour of ZrO2 honeycomb sandwich structures prepared by DLP stereolithography

The ceramic honeycomb sandwich structures of 3 mol% yttria-stabilized tetragonal ZrO2 (3Y-TZP) material were fabricated by an additive manufacturing technique based on the digital light processing (DLP) system. The bending behaviour of hexagonal and square honeycomb sandwich structures was investigated with three-point bending test. The effects of geometric parameters, including the thickness of the face-sheet, the height of the cell, the thickness of the cell wall and the size of the cell, were studied through experiments carefully. The results illustrated that the bending strength of the ceramic honeycomb sandwich structure can reach 170 MPa at a relative density of 41.72%. The geometric parameters of the honeycomb core were more critical than the sandwich face-sheet. The cell size, cell wall thickness and cell height were found to be the preferred geometric parameter for justifying the bending resistance performance of the ceramic sandwich panel. Square honeycomb demonstrated better bending performance than the hexagonal honeycomb. This study provides a new basis for further studies on the ceramic lightweight structures.

Hot-corrosion resistance and phase stability of Yb2O3–Gd2O3–Y2O3 costabilized zirconia-based thermal barrier coatings against Na2SO4 + V2O5 molten salts

The hot corrosion behavior of plasma-sprayed Yb2O3-Gd2O3-Y2O3 co-doped ZrO2 (YGYZ) coating against Na2SO4 + V2O5 molten salts was investigated and its detailed hot corrosion mechanism was suggested. The chemical reactivity order between the stabilizers was proposed based on the electronic structure and Lewis acid-base mechanism. After hot corrosion, the YGYZ coating exhibited the maintenance of tetragonality ratio and relatively lower extent of destabilization less than 40% of conventional yttria-stabilized ZrO2 coating. These great chemical and phase stabilities imply that YGYZ is promising candidate for high-temperature thermal barrier material.