Ceramic Films Research Articles

Ultra-low-cost, flexible and durable electrochromic tape device based on aluminum foil

Electrochromic devices (ECDs) have the ability to selectively change their color state. They come in many forms, such as smart windows, e-ink displays and recently even as flexible tapes. Since most of ECDs incorporate traditional “sandwich” architecture, which requires at least one electrode to be made of a transparent conductive polymer or thin film ceramics, they are considered too expensive and fragile compared to devices made from metal or alloy foils. For the first time, we present a true low-cost, flexible and durable ECD tape that uses a common “kitchen-grade” aluminum foil for electrodes, while employing a Li-WO3 intercalation based electrochromic system. The presented ECD tape is capable of showing two color states. The tested tapes were up to 20 cm long but could be easily made longer due to their “inverted sandwich” architecture. Due to the absence of transparent counter electrode, the assembled ECD tape has excellent durability properties and could be used in color changing clothes, adaptive camouflage or other applications.

Garnet transparent ceramic film of Y3Al5O12:Eu3+ fabricated through an interface reaction of layered rare-earth hydroxide nanosheets on amorphous alumina

Traditional preparation of yttrium aluminum garnet (YAG) transparent ceramics involves the steps of powder preparation, green body formation and sintering. It is not only time-consuming, high energy consumption and high cost, but also has high requirements for equipment. Here, we developed a special interface reaction to prepare YAG transparent ceramic film. Transparent ceramic fluorescent film composed of YAG: Eu3+ was prepared by spin-coating the exfoliated layered rare earth hydroxide (LRH) nanosheets on the amorphous alumina substrate, followed by sintering at 1500 °C for 2 h in air. Al element tends to diffusion to the rare earth oxide side for the interface reaction, and more Al participates in the reaction at a higher temperature. The higher temperature makes more amorphous Al2O3 gradually participate in the interface reaction, and react with (Y0.95Eu0.05)2O3 to form mesophases of (Y0.95Eu0.05)4Al2O9 and (Y0.95Eu0.05)AlO3 at temperature lower than 1500 °C, and finally to form (Y0.95Eu0.05)3Al5O12 (YAG: Eu3+) at 1500 °C. The fluorescent film exhibited red emission at 618 nm, which is different from the orange red emission for YAG: Eu3+. The red emission at 150 °C maintained over 85% intensity of that at room temperature. We believe that the outcomes of this work may enrich the applications of the LRH nanosheets and may have wide implications to other compositional transparent ceramics.

Large energy storage density and electrocaloric strength of Pb0.97La0.02(Zr0.46-xSn0.54Tix)O3 antiferroelectric thick film ceramics

Pb0.97La0.02(Zr0.46-xSn0.54Tix)O3 (PLZST, x = 0.04, 0.06, 0.08, 0.15, and 0.18) antiferroelectric thick film ceramics were fabricated via a tape-casting approach. The energy storage performance and electrocaloric effect (ECE) were investigated in terms of the measurements on the hysteresis loops and Maxwell relation. The maximum value of energy storage density of 5.2 J/cm3 and efficiency of 78.2% were procured at 600 kV/cm in Pb0.97La0.02(Zr0.42Sn0.54Ti0.04)O3 thick film ceramics at room temperature. In addition, the ECE was indirectly calculated using the Maxwell relation and the polarizations extracted from the P-E loops as a function of temperature and electric field, an adiabatic temperature change of ΔT = 2.47 °C was procured in Pb0.97La0.02(Zr0.42Sn0.54Ti0.04)O3 thick film ceramics at 500 kV/cm, corresponding to the calculated electrocaloric strength of 0.48 K(MV/m)−1. These results indicate that the PLZST thick film ceramics are promising for practical applications in high-power energy storage capacitors and solid-state refrigeration devices.

Synthesizing Superior Flexible Oxide Perovskite Ceramic Nanofibers by Precisely Controlling Crystal Nucleation and Growth.

Oxide perovskite ceramics are cornerstone materials of electronic devices, but they easily break under bending. Such brittle failure phenomenon limits their applications in emerging flexible electronics. Here, the authors propose a scalable approach of sol-gel electrospinning to synthesize flexible perovskite Li0.35 La0.55 TiO3 (LLTO) nanofibers (NFs) by reducing grain sizes and pore defects in the NFs. The strategy is to precisely control crystal nucleation and growth by forming homogeneous nuclei in the sol before electrospinning and to construct soft twin and amorphous grain boundaries by controlling calcination temperatures. Ball-milling the sol promotes the formation of numerous LLTO nuclei and thus effectively refines grains, while using gradient calcination temperatures from 200 to 900°C creates intricate soft grain boundaries. The individual LLTO NF shows ceramic toughness with an elastic modulus of ≈40GPa and the NF film demonstrates silk-like softness with a large elastic strain of 1.51%. Moreover, the LLTO film shows superior fatigue resistance and it maintains structure well after repeated tensile-buckling cycles at 40% strain. The proposed strategy facilitates to develop flexible oxide perovskite ceramic films with appealing applications.

Mechanical properties of biomimetic ceramic with Bouligand architecture

AbstractBiomimetic Bouligand architecture is constructed in the ceramic to improve its toughness. Firstly, unidirectional carbon fiber‐reinforced ZrB2‐SiC ceramic films are achieved through a vacuum‐assisted filtration method using graphene oxide. Then, ceramic films are helically assembled at a fixed angle of 30° in the graphite die based on the fiber orientation. Finally, the spark plasma sintering method was utilized to densify helical assembly carbon fiber/ceramic films. By constructing Bouligand structure, high fracture toughness (7.4 MPa·m0.5) and work of fracture (∼1055 J/m2) are achieved in ZrB2‐based ceramic. The toughening mechanisms mainly are crack deflection, twisting and branching, carbon fiber pulling out, and bridging.

P040 INFLAMMATORY REACTION TO ALD COATED POLYPROPYLENE MESHES USED FOR HERNIA REPIAR. AN EXPERIMENTAL STUDY IN ANIMALS

Abstract Aim The main goal of the present work is to study and ability of Atomic Layer Depostion (ALD) ultra-thin (<100nm) ceramic films on polypropylene (PP) hernia meshes to prevent the mesh-associated infections (post-surgery complications). Material and Methods Three types of ALD nanofilms were examined: Al2O3, TiO2, or TixVyOz. 10 rats and 5 rabbits were used to evaluate the tissue reaction of surface modified PP meshes and for biomechanical (antibacterial, inflammation effect), biocompatibility, and barrier testing of the healed tissue. The ALD coated PP meshes were implanted into rabbits and rats together with uncoated ones. After 10, 20, 30 and 60 days, the hernia meshes with the surrounding soft tissues were removed and fixed for histological and cytological studies. Results The TixVyOz (28nm) film showed enhanced antibacterial activity compare to Al2O3 and TiO2 films. The histology was performed on coated and uncoated PP mesh samples. Conclusions The ALD TixVyOz film helped to avoids formation of rough scar tissue (microscale roughness, which prevents ability biofilm formation) and, reduction of eosinophilic-cell and lymphocytic-cell reactions of the tissues surrounding the mesh, illustrate good integration into the surrounding tissue with minimal inflammatory reaction and minimal adhesions to intra-abdominal structures. The ALD film was highly effective in inhibiting S. aureus and E. coli bacteria adhesion and exhibited excellent biological activity in promoting osteoblastic adhesion. Speculatively, presence of vanadyl (≡V=O:) chemical groups, either on the surface or in the bulk, believe to play a key role in high performance of the TixVyOz compare to TiO2.

Advanced electrodes for electrochemical energy storage and conversion devices fabricated by reactive spray deposition technology

While different electrochemical devices require electrodes with different microstructures, thicknesses, and catalyst compositions, the reactive spray deposition technology (RSDT) process has been able to demonstrate flexibility to provide what is needed for each application. From developing porous electrodes with platinum group metal catalysts for fuel cell and electrolysis applications, to the fabrication of dense ceramic thin films for solid oxide fuel cell electrolytes, to the fabrication of novel electrodes for rechargeable lithium-ion batteries, the RSDT can be modified to fabricate these layers in a one-step process. Using a combustion flame, the heat generated from the flame is used to provide the energy for sintering ceramic particles into a dense layer and it can be used to decompose a precursor solution into a catalyst particle that contains the desired stoichiometry. The RSDT process has been shown to be an effective method for the development of electrode thin films.

Nonclassical Crystallization of an Al2O3 Film by Positively Charged Secondary Nanoparticles during Aerosol Deposition

Thin film growth through nonclassical crystallization with charged nanoparticles as building blocks has been studied in chemical vapor deposition and physical vapor deposition. A similar mechanism might be applied to aerosol deposition (AD), with which the mechanism for the evolution of dense ceramic films at room temperature has not been clearly understood. Aerosol particles fracture into fragments of secondary nanoparticles during AD. In this work, secondary particles passing between the two parallel biased and grounded electrodes were captured by the transmission electron microscopy (TEM) grid membrane on each electrode, and it was revealed that they were mainly positively charged. Neutral secondary nanoparticles, not deflected by the electric field, produced a porous film on the silicon substrate, whereas charged secondary nanoparticles produced a dense film. The positive charge of the secondary nanoparticles appeared to enhance the plastic deformation required for the evolution of dense films during AD, which was supported by ab initio calculations.

Cu-Mn Co-doped NiFe2O4 based thick ceramic film as negative temperature coefficient thermistors

NTC (Negative Temperature Coefficient) thermistors are widely used as temperature sensors in industrial and medical applications due to their high-temperature sensitivity, durability, and low cost. Generally, NTC thermistors are made from spinel structured ceramics formed by transition metal oxides with the general formula AB2O4. One of the spinel structured ceramics that can be made for NTC thermistors is NiFe2O4 nanoparticles. This work aimed to prepare Cu-Mn co-doped NiFe2O4 based thick ceramic film using Jarosite mineral as a precursor. The synthesis method used was a simple coprecipitation method, while the technique used in making a thick ceramic film was a simple screen printing technique. The sintering temperatures used were 1000 °C, 1100 °C, and 1200 °C. Based on x-ray diffraction analysis, the thick films consist of spinel phase, hematite phase, and some unidentified phase. The constant thermistor values (B) for thick films obtained with 1000, 1100, and 1200 °C sintering temperatures were 4740 K, 5669 K, and 5731 K, respectively. These results showed that all obtained thick films had passed the minimum value in market needs (B ≥2000 K).

Analysis of High-Throughput Electrochemical Impedance Spectroscopy via Hierarchical Bayesian Models

Electrochemical impedance spectroscopy (EIS) is a powerful characterization technique that enables in-situ investigation of electrochemical processes over a wide range of timescales, making it particularly effective in analysis of electrochemical energy conversion devices such as fuel cells and batteries. The advent of automated high-throughput EIS systems presents an exciting opportunity for materials discovery, rapidly providing detailed information about candidate materials. However, the utility of EIS as an electrochemical method is paralleled by the complexity of interpreting the resulting data: overlapping features, noise, and measurement artifacts make EIS spectra notoriously difficult to analyze. Equivalent circuit models (ECMs) are widely used to deconvolute EIS data, but there is significant ambiguity in model selection; meanwhile, the distribution of relaxation times (DRT) has become increasingly popular as an alternative/complementary deconvolution method, but faces similar uncertainty in the choice of regularization parameters. The sheer volume of data produced by high-throughput methods amplifies these challenges, necessitating automated, self-consistent analysis procedures.Here, we discuss high-throughput EIS characterization of protonic ceramic electrode thin films and demonstrate the application of hierarchical Bayesian models for robust analysis of the data. The calibrated hierarchical Bayesian DRT resolves much of the ambiguity in regularization parameters by encoding desired properties of the DRT in prior distributions [1]. Meanwhile, the versatility of the DRT enables appropriate deconvolution of thousands of spectra without predetermined model selection. The DRT may be translated to an ECM for further quantitative analysis of individual relaxation timescales and magnitudes by leveraging a flexible semi-empirical model. In addition, advanced Bayesian DRT models can be implemented to address outliers, sample drift, and multi-spectrum deconvolution. These tools enable conversion of raw spectra to a dataset amenable to further interpretation via machine learning and other methods, thereby expanding opportunities to distill meaningful insight from high-throughput electrochemical studies.

Semi‐Automatic Deposition of Oriented Cu(OH)2 Nanobelts for the Heteroepitaxial Growth of Metal–Organic Framework Films

AbstractProcessing oriented metal–organic frameworks (MOFs) as thin films is a key challenge for their application to device fabrication. However, typical fabrication methods cannot generate precisely oriented crystals on commercially relevant scales (i.e., cm2). This limits access to applications that require anisotropic functional properties (e.g., separation, optics, and electronics). Currently, highly oriented copper‐based MOFs are synthesized via the addition of the organic MOF component to an ethanolic solution of manually aligned Cu(OH)2 nanobelt films. In this work, the optimization of a semi‐automatic method for the fabrication of precisely oriented MOF films that affords a 100% yield of high quality ceramic films at the centimeter scale is reported. This improved fabrication protocol will facilitate the progress of heteroepitaxially grown MOFs for molecular separators and micro‐opto‐electronic devices.

Exploring the structural uniformity and integrity of protonic ceramic thin film electrolyte using wet powder spraying

Thin protonic ceramic electrolyte contributes to lower ohmic resistance and enhances electrochemical performance of protonic ceramic electrochemical cells. However, manufacturing of large-scale thin electrolyte remains a challenge. Wet powder spraying is an attractive technique to deposit <10 μm thin electrolyte when advanced atomizing techniques and optimized spraying process are integrated. Here ultrasonic atomization is integrated in the wet powder spray technique to reduce the thickness of electrolyte. Moreover, a parametric study is conducted to optimize the wet powder spray process to deposit uniform and crack-free electrolyte film. It is illustrated that tuning of solid loading rates and spray passes can affect the morphology of the as-sprayed electrolyte film, enabling the structural compactness of the sintered electrolyte layer. To maintain chemical stability of the electrolyte layer during sintering, effect of sintering temperature is further investigated to produce a physically thin, structurally dense, and chemically homogeneous electrolyte layer. The protonic ceramic electrochemical cells fabricated with optimized spraying and sintering parameters demonstrate excellent performance under both fuel cell and electrolysis modes. In addition, the cells exhibit remarkable structural integrity during redox and long-term stability tests. • A wet powder spraying technique was integrated into the manufacturing of protonic ceramic electrochemical cells. • Solid loading rates, spray passes, and sintering temperatures were explored and optimized. • PCECs with a 7-μm thick BZCYYb electrolyte were successfully fabricated and demonstrated good structural uniformity and electrochemcial performance.

High-temperature superconducting CORC® wires with record-breaking axial tensile strain tolerance present a breakthrough for high-field magnets

Cuprate high-temperature superconductors (HTS), such as RE-Ba2Cu3O7−δ (REBCO, RE = rare earth), (Bi,Pb)2Sr2Ca2Cu3O10−x and Bi2Sr2CaCu2O8−x , have enabled the development of high-field superconducting magnets capable of generating magnetic fields far exceeding 20 T. The brittle nature of HTS requires elaborate means to protect them against the high stresses and strains associated with high-field magnet operation, and so far, has prevented reliable high-field HTS magnets from becoming a reality. Here we report a more than tenfold increase in the irreversible strain limit under axial tension (ϵ irr) to over 7% in optimized high-current conductor on round core (CORC®) conductors, compared to the REBCO tapes from which the CORC® conductor is wound. Minimizing the tape winding pitch of the helical wind mechanically decouples the brittle REBCO film from the overall conductor. The REBCO tapes behave as springs, limiting the rate at which applied strain is transferred to the ceramic film. In addition, high-strength alloy cores allow the critical stress (ϵ crit) under axial tension at which initial degradation of CORC® conductors occurs to exceed 600 MPa, making them one of the strongest superconductors available. Mechanically decoupling the ceramic REBCO films from the overall CORC® conductor allows effective protection against the high operating stresses in high-field magnets. This breakthrough presents a monumental shift for HTS magnet technology, bringing reliable high-field superconducting magnets for compact fusion machines, the next generation of particle accelerators, and 40–60 T research solenoids within reach.

Electrical Properties of Aluminum Oxide Ceramics Film on a Metal

Electrical Properties of Aluminum Oxide Ceramics Film on a Metal

Making powder aerosol deposition accessible for small amounts: A novel and modular approach to produce dense ceramic films

AbstractPowder aerosol deposition is a promising technique to deposit dense ceramic films directly at room temperature. While previous developments pointed towards larger and more complex deposition devices, this work follows a different approach and proposes a simplified and miniaturized coating device (denoted as Micro‐PAD, µPAD). The aim is twofold: creating a smaller and flexible device consisting of an aerosol generation unit and a deposition chamber with a combined low areal footprint of 30 cm by 20 cm (that, e.g., easily fits in a glove box) as well as lowering the hurdle for other researchers to use the powder aerosol deposition. Therefore, we introduce a device mainly based on commercially available components/connectors as well as manual operated valves/flow meters. A key point is the elimination of moving components by just using a spot deposition that was enabled by using a circular de‐Laval‐type nozzle.The operational capability of µPAD is proven for the deposition of alumina films and compared to conventional PAD in terms of mechanical, crystalline, and optical film properties. Thick films with a bell‐shape‐like profile are deposited by µPAD, featuring a plateau in the center of the film with a diameter of 5 mm and a FWHM (full width at half maximum) diameter of about 10 mm. Alumina films produced by µPAD do not only match the properties of corresponding PAD films, but oftentimes outperform them. Here, µPAD films exhibit increased hardness and optical transmittance values, surpassing reference values of the conventional sprayed counterparts by at least 10%. Also, film integrity and adhesion to the substrate are slightly higher in case of µPAD. Reasons for the improved film properties are found by X‐ray diffraction, with a significantly higher fracturing of impacting particles during µPAD combined with improved film consolidation as observed by SEM. Furthermore, µPAD featured doubled to tripled the deposition rates and, markedly almost doubled the deposition efficiency.

Design and 3D Printing of Controllable and Gradient Porous Supports for Solid Oxide Fuel Cells

A controllable and gradient porous structure is desirable for many applications including solid oxide fuel cells (SOFC) electrodes. A SOFC contains a minimum three basic ceramic thin films with a thin yet dense electrolyte layer separates the adjacent porous anode and cathode layers. In general, the thinner the electrolyte layer, the smaller the ohmic resistance would be. The anode and cathode layers need to be porous so to allow gases (e.g. H2 and O2) to easily penetrate to the triple-phase boundary (TPB). At the same time the anode and cathode layers serve as the paths of removing the electrons generated at the TPBs. Properly design and fabricated porous electrode microstructure could greatly increase the connectedness of gas, electrons and/or protons/oxygen ions, and therefore reduce the gas diffusion and ohmic resistances of the SOFC electrodes and boost the overall fuel cell performance.Although there are electrolyte- and cathode- supported SOFC developers, the most used configuration is anode-supported or additional component-supported, for example metal-supported or ceramic-supported with a planar or tubular geometry. Conventionally, the porosity is generated by using sacrificial templates or pyrolyzable pore-formers for pore formation. Pores are formed after the burning off these sacrificial templates or pyrolyzable pore-formers at elevated temperatures. The size, shape and amount of the pore-formers can be controlled. However, the connectivity and orientation of these pores are not easily controllable, leaving significant amount of closed and isolated pores. These isolated and/or closed pores do not contribute to the TBP. Freeze casting of water-based suspension slurries could generate aligned pores, the low connectivity and weak mechanical strength challenges remain.This paper focuses on the design and fabrication of a desired gradient porous microstructure for use as a SOFC support. The pore size and shape, porosity and connectivity could be determined and strictly controlled by design. Tubular and planar parts with metal, cermet and/or ceramic materials are to be fabricated. Additive manufacturing (AM, or 3D printing) process enables the fabrication of the complicated parts with the desired microstructure directly from the computer-aided design (CAD) models. The morphology, porosity, permeability and tortuosity of the 3D printed parts are investigated and results are discussed.

Fabrication and Characterization of Functional Ceramic Films by Solution Spray Pyrolysis: Correlations with the Thermal Decomposition Characteristics of the Constituent Salts

Thin films of ceramic or ceramic-metal (cermet) electrodes with appropriate structure and morphology are always sought in ceramic fuel cells and electrolyzers. These films can serve as either electrodes or electrolytes in solid oxide fuel cells (SOFCs) or electrolyzers (SOECs) requiring different morphological and structural characteristics for optimal function. Thus, electrode parameters such as thickness, porosity and tortuosity essentially determine the values of gaseous effective diffusivities and subsequently the extent of concentration polarization losses [1]. In addition, nanostructured thin film electrodes have shown enhanced conversion efficiencies compared to their bulk materials counterparts, essentially leading to low polarization losses [2].On the other hand, the electrolyte has to possess minimal porosity not allowing mixing between the anode and cathode compartments and adequately blocking electronic transport. Low thicknesses are desirable for minimization of the cell’s total ohmic resistance. However, at low electrolyte thicknesses, total ohmic cell polarization is affected by electrode microstructure to a greater extent than by electrolyte ohmic resistance due to contiguity factors between metal particles in the fabricated cermets and metal depletion in the anode functional layer [3].Generally, for a given set of chosen materials, all of the above microstructural requirements for electrodes and electrolytes have to be met by the adopted fabrication methods which have to be subsequently optimized with respect to their operational parameters. It is advantageous to resort to the so called innovative fabrication methods for the above, in particular for their functional components. The term refers to methods with the potential of producing nanostructural components and controlling in situ the film’s characteristics such as porosity, pore size, thickness and uniformity.The solution spray pyrolysis technique (SSP) belongs to this family of methods as it is based on molecular deposition and it involves spraying of a solution of suitable constituent metal salts onto a heated substrate [4].The technique is robust, environmentally friendly if water is used as solvent, easily upscalable and with easily controllable processing parameters. It also possesses the potential of producing very thin layers of components (i.e. < 1 μm) and therefore, reducing the subsequent sintering temperatures due to the more active precursor components of the constituent particles forming the final film.In a recent publication [4], we have shown that the technique can be optimized in terms of deposition temperature, time and concentration of the precursor salts in order to fabricate crack-free films of La0.75Sr0.25MnO3 (LSM) and CuO-CeO2 on dense YSZ substrates with thicknesses of the order of 0.65–3.5 μm. Cu-CeO2 constitutes a potential anode that combines the functionalities of copper ( an electronic conductor) and a good oxidation catalyst (i.e. CeO2) for potential hydrocarbon fuels fed into a SOFC while LSM is the typical state of the art cathode used with a YSZ electrolyte [5]. It was shown that lower deposition temperatures (but above the solvent boiling point) generally lead to more porous films and the precursor salt concentration is coupled with the optimal deposition temperature range and deposition time. In the present communication, we extend these findings in order to include films of Gadolinia (10mole%) stabilized Ceria (CGO10) on dense Zr0.92Y0.08O2 - x (YSZ) and La0.3Sr0.7FeO3 (LSF70) substrates. CGO10 is a typical solid electrolyte more suitable for intermediate temperature applications (i.e. 500-750°C) and it is amenable to being fabricated with lower porosities by SSP than YSZ [6]. Focus is on the thermal characteristics of the constituent salts with respect to correlations with the appropriate deposition temperatures as well as the effect of deposition time. The produced films are characterized by X-ray diffraction and scanning electron microscopy (SEM). CGO10 films were also characterized in terms of their electronic blocking capability in contact with the LSF70 substrates.

Instability of residual stress of crystalline and glass oxide thin films prepared by sol-gel method

Previously, we demonstrated that sol-gel-derived glass and ceramic thin films show a decrease in in-plane residual tensile stress during storing in humid atmosphere at room temperature. To clarify the mechanism, we prepared SiO2 glass films on Si(100) wafers via spin-coating followed by firing and obtained in-plane stress by measuring the substrate curvature. The SiO2 film fired at 600 °C showed a decrease in tensile stress during storing but showed recovery when heated afterward at 300 °C. We detected an increase in the infrared O–H absorption peak area as well as in the film thickness during storing, the latter of which was detected by in situ ellipsometry for the SiO2 film fired at 600 °C. On the other hand, when fired at 880 and 885 °C, the SiO2 films gained “compressive” residual stress, which slightly increased with time during storing. Based on these observations the decrease in tensile stress during storing has been confirmed to be caused basically by the film expansion induced by water adsorption. The SiO2 film fired at 600 °C showed recovery in stress on heating at 300 °C, which was incomplete in contrast to the CeO2 film that showed complete recovery as reported previously. Such recovery in stress was accompanied by decrease and turning back of the O–H absorption peak are to original values, the latter of which was incomplete in the SiO2 film but complete in the CeO2 film. These results on stress recovery and IR absorption suggest that besides water “adsorption,” water “absorption” cannot be ruled out for the SiO2 film as the partial cause of the decrease in “tensile” stress during storing.

Constrained sintering of alumina micro-ring films on stiff and compliant substrates: Constriction or dilation?

The sintering behavior of ring-shaped alumina films on different types of substrates (polished sapphire and platinum coated sapphire) has been investigated. Variation of substrate material, layer thickness and heating schedule led to different interface properties which were quantified using the interfacial friction parameter as a measure of the slip distance of the free edge. This interfacial friction implies the compliance of the film-substrate interface, thus allowing the quantification of the ability of the free edges to slide along the substrate. Ring structures were made with outer radii of 100 –500 µm and the ratios of inner to outer radii were 0.1 (broad ring segment with small inner hole) and 0.4 (narrow ring segment with big inner hole). During sintering, the outer film edge was found to recede in all systems, whereas the behavior of the free edge located at the inner hole was strongly dependent on the interfacial friction. When sintering of alumina micro-rings were carried out on sapphire substrate, a high interfacial friction resulted in the positive displacement of the inner edge, causing the inner hole to open. Sapphire substrates coated with platinum offered a lower interfacial friction resulting in the opening of the hole in a more distinct manner as compared to the uncoated sapphire substrates. As the thickness of the film also affects the interfacial friction, a thicker film (27 µm) on platinum coated substrate had very low friction. This resulted in a negative displacement of the inner ring leading to closing of the hole. These effects are in qualitative agreement with the predicted analytical model for constrained sintering of annular ceramic films. A combination of film thickness, substrate material and aspect ratio of the ring either leading to constriction or dilation of the annular alumina film were carefully investigated.

Fabrication and Characterization of Functional Ceramic Films by Solution Spray Pyrolysis: Correlations with the Thermal Decomposition Characteristics of the Constituent Salts

Thin films of ceramic or ceramic-metal (cermet) electrodes with appropriate structure and morphology are always sought as either electrodes or electrolytes in solid oxide fuel cells (SOFCs) or electrolyzers (SOECs) requiring different morphological and structural characteristics for optimal function. Requirements for the electrodes and electrolytes differ in each case and these dictate operational conditions of the adopted fabrication methods. The solution spray pyrolysis fabrication technique (SSP) is based on molecular deposition and it involves spraying of a solution of suitable constituent metal salts onto a heated substrate. In the present communication, we use this technique to fabricate thin films of Gadolinia (10mole%) stabilized Ceria (CGO10) on dense Zr0.92Y0.08O2-x (YSZ) and La0.3Sr0.7FeO3 (LSF70) substrates and La0.75Sr0.25MnO3 (LSM) and CuO-CeO2 on dense YSZ substrates. Focus is on the thermal characteristics of the constituent salts with respect to correlations with the appropriate deposition temperatures as well as the effect of deposition time.