High-Temperature Electrical Insulation Behavior of Alumina Films Prepared at Room Temperature by Aerosol Deposition and Influence of Annealing Process and Powder Impurities

Schubert, Michael; Leupold, Nico; Exner, Jörg; Kita, Jarosław; Moos, Ralf

doi:10.1007/s11666-018-0719-x

Cited by 25 publications

(8 citation statements)

References 37 publications

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“…[ 1 ] Due to the worldwide development of this process method, different names like aerosol deposition (AD), [ 2 ] vacuum kinetic spray (VKS), [ 3 ] vacuum cold spray (VCS), [ 4 ] granule spray in vacuum (GSV), or nanoparticle deposition system (NPDS) [ 5 ] are used by different research groups. The variety of suitable ceramics ranges from insulator materials like Al 2 O 3, [ 6 ] dielectric materials like BaTiO 3 and Bi 4 Ti 3 O 12 , [ 7 ] solid electrolytes for proton conducting fuel cells like Ba(Zr, Sn, Ce)O 3 , [ 8–10 ] all‐solid‐state battery electrolytes like Li 7 La 3 Zr 2 O 12 , [ 11 ] sensor materials [ 12 ] and lunar regolith [ 13,14 ] for futuristic applications in space to thermoelectric films like CuFeO 2 . [ 15 ] Thermoelectric materials enable the direct emission‐free conversion of thermal to electrical energy and vice versa.…”

Section: Introductionmentioning

confidence: 99%

Laser‐Annealing of Thermoelectric CuFe_0.98Sn_0.02O₂ Films Produced by Powder Aerosol Deposition Method

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Kita

Moos

et al. 2020

Adv Materials Inter

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of thermal to electrical energy and vice versa. The state-of-the-art material for thermoelectric generators (TEG) is bismuth telluride (Bi 2 Te 3); however, its application is limited due to its high costs and tendency to oxidize at elevated temperatures. Copper-iron-oxides are a thermally stable promising alternative due to the low costs of the raw materials, their high Seebeck coefficient, and their high electrical conductivity. The PAD method enables to form dense nanocrystalline ceramic films on a variety of substrates with high deposition rates. [16-18] In contrast to all other ceramic processing routes, even moisture-sensitive ceramics, or ceramics with high sintering temperatures can be fabricated at room temperature (RT). [11] Besides the dry ceramic powder, neither additional binders nor other liquids are needed. The ceramic particles are accelerated towards a substrate by a pressure difference. The kinetic energy of the particles is converted into bonding energy during their impact on the substrate and comes along with the reduction of the crystallite size and formation of microstrain within the atomic lattice. [19-21] Particle fracturing occurs along the grain boundaries and within the grains generating temporarily unsaturated surface bonds that cause an excellent adherence of the particles. [22] Despite all the positive aspects of the powder aerosol deposition summarized in Figure 1, a major disadvantage in the as-deposited state that all PAD films have in common is the reduced electrical conductivity of the films. A thermal annealing step is necessary to reduce the mechanical stress of the film and to restore the electrical properties so that they reach bulk values. Exner et al. recently found out that the required annealing temperature in the furnace depends on the melting point of the functional ceramic materials, though it is significantly lower than the typical sintering temperatures. [23] In contrast, laser-based annealing could provide additional advantages like a reduced annealing time or a targeted local property change as it was shown by Palneedi et al. for PZT (Pb(Zr,Ti)O 3) [24-30] and Shinonaga et al. for TiO 2. [31-33] In this study, we investigated the influence of laser irradiation on the properties of a nanocrystalline thermoelectric film. Tin doped copper-iron-oxide respectively copper delafossite (CuFe 0.98 Sn 0.02 O 2), which is known for its good thermoelectric properties and is processability by PAD, [15,34] was synthesized by the mixed-oxide-route. Films were fabricated by powder aerosol deposition method. After deposition, the films were annealed with a frequency tripled Nd:YAG laser (λ = 355 nm) and its influence on the microstructure and the electrical properties was examined by optical and electrical measurements. Powder aerosol deposition (PAD) is a unique coating method that allows the fabrication of dense ceramic films on a variety of substrates at room temperature. This spraying process can produce film thicknesses of several micrometers within minutes without the use of...

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Section: Introductionmentioning

confidence: 99%

Laser‐Annealing of Thermoelectric CuFe_0.98Sn_0.02O₂ Films Produced by Powder Aerosol Deposition Method

Nazarenus

Kita

Moos

et al. 2020

Adv Materials Inter

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“…Several up-to-now-used AD materials, mainly metal oxides resemble lunar soil or dust in their particle size distributions [15,22]. Examples for the successful application of the AD method for the processing of metal oxide powders include, e.g., Fe 2 O 3 [23], SiO 2 [24,25], TiO 2 , [26,27], and Al 2 O 3 [16,28,29], or high temperature superconductors [30]. To the best of the authors’ knowledge, AD is the only process to produce dense ceramic coatings in the specified particle size range directly from dry powder and without any heat treatment.…”

Section: Introductionmentioning

confidence: 99%

Manufacturing Dense Thick Films of Lunar Regolith Simulant EAC-1 at Room Temperature

et al. 2019

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The Aerosol Deposition (AD, also known as gas kinetic spraying or vacuum deposition) method is a rather novel coating process to produce dense thick films directly from dry ceramic (or metal) powders on a variety of substrates without any heat treatment. Because of the similarity of the up to now used powders and lunar regolith, it is imaginable to use AD systems for future in situ resource utilization missions on the Moon planned by several space agencies. To test the feasibility of such an endeavor, the processability of lunar mare simulant EAC-1 by the AD method has been examined in this study. Three regolith films with an area of 25 × 10 mm2, and thicknesses between 2.50 µm and 5.36 µm have been deposited on steel substrates using a standard AD setup. Deposited films have been investigated by Laser Scanning Microscopy (LSM) and Scanning Electron Microscopy (SEM). Moreover, the roughness and Vickers hardness of the deposited films and the underlying substrates have been measured. It has been shown that dense consolidated films of regolith simulant can be produced within minutes by AD. The deposited films show a higher roughness and, on average, a higher hardness than the steel substrates. Since on the Moon, naturally available regolith powders are abundant and very dry, and since the required process vacuum is available, AD appears to be a very promising method for producing dense coatings in future Moon exploration and utilization missions.

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“…However, the resistance of the electrode contribution significantly increased, especially visible at 600 °C where the low-frequency CPE resistance is about a factor of ten larger during cooling. Although not completely understood yet, this behavior is thought to be connected to a reduction of the parasitic electronic film conductivity caused by a heat treatment, as observed by Schubert et al for AD alumina films [16]. The ionic conductivity σ was calculated using the described geometry of the interdigital electrodes [17] and a GDC10 film thickness of 1.2 µm.…”

Section: Resultsmentioning

confidence: 99%

Annealing of Gadolinium-Doped Ceria (GDC) Films Produced by the Aerosol Deposition Method

et al. 2018

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Solid oxide fuel cells need a diffusion barrier layer to protect the zirconia-based electrolyte if a cobalt-containing cathode material like lanthanum strontium cobalt ferrite (LSCF) is used. This protective layer must prevent the direct contact and interdiffusion of both components while still retaining the oxygen ion transport. Gadolinium-doped ceria (GDC) meets these requirements. However, for a favorable cell performance, oxide ion conducting films that are thin yet dense are required. Films with a thickness in the sub-micrometer to micrometer range were produced by the dry room temperature spray-coating technique, aerosol deposition. Since commercially available GDC powders are usually optimized for the sintering of screen printed films or pressed bulk samples, their particle morphology is nanocrystalline with a high surface area that is not suitable for aerosol deposition. Therefore, different thermal and mechanical powder pretreatment procedures were investigated and linked to the morphology and integrity of the sprayed films. Only if a suitable pretreatment was conducted, dense and well-adhering GDC films were deposited. Otherwise, low-strength films were formed. The ionic conductivity of the resulting dense films was characterized by impedance spectroscopy between 300 °C and 1000 °C upon heating and cooling. A mild annealing occurred up to 900 °C during first heating that slightly increased the electric conductivity of GDC films formed by aerosol deposition.

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High-Temperature Electrical Insulation Behavior of Alumina Films Prepared at Room Temperature by Aerosol Deposition and Influence of Annealing Process and Powder Impurities

Cited by 25 publications

References 37 publications

Laser‐Annealing of Thermoelectric CuFe_0.98Sn_0.02O₂ Films Produced by Powder Aerosol Deposition Method

Laser‐Annealing of Thermoelectric CuFe_0.98Sn_0.02O₂ Films Produced by Powder Aerosol Deposition Method

Manufacturing Dense Thick Films of Lunar Regolith Simulant EAC-1 at Room Temperature

Annealing of Gadolinium-Doped Ceria (GDC) Films Produced by the Aerosol Deposition Method

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High-Temperature Electrical Insulation Behavior of Alumina Films Prepared at Room Temperature by Aerosol Deposition and Influence of Annealing Process and Powder Impurities

Cited by 25 publications

References 37 publications

Laser‐Annealing of Thermoelectric CuFe0.98Sn0.02O2 Films Produced by Powder Aerosol Deposition Method

Laser‐Annealing of Thermoelectric CuFe0.98Sn0.02O2 Films Produced by Powder Aerosol Deposition Method

Manufacturing Dense Thick Films of Lunar Regolith Simulant EAC-1 at Room Temperature

Annealing of Gadolinium-Doped Ceria (GDC) Films Produced by the Aerosol Deposition Method

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Laser‐Annealing of Thermoelectric CuFe_0.98Sn_0.02O₂ Films Produced by Powder Aerosol Deposition Method

Laser‐Annealing of Thermoelectric CuFe_0.98Sn_0.02O₂ Films Produced by Powder Aerosol Deposition Method