Fabrication of Scandia-Stabilized Zirconia Thin Films by Instant Flash Light Irradiation

Abstract

In this study, scandia-stabilized zirconia (ScSZ) electrolyte thin-film layers were deposited via chemical solution deposition (CSD). We selected 10ScSZ (10% Sc 2 O 3 , 90% ZrO 2 molar ratio) as the target material, and the precursor solution was prepared by precise calculations. The 10ScSZ solution was deposited on Al 2 O 3 substrate using a spin-coating method. Then, the substrate was sintered using two methods: flash light irradiation and thermal. The characteristics of the thin films were compared, including ionic conductivity, surface morphology, and chemical composition. Pulsed light sintering was applied in the sintering step under a variety of energy density conditions from 80 to 130 J/cm 2 , irradiation on/off times of 10 ms and 10 ms/500 ms, number of pulses, and bottom heat from 300 to 600 • C. The ionic conductivity of the ScSZ electrolyte layers fabricated by thermal or flash light irradiation methods was tested and compared. The results show that the ScSZ electrolyte layer sintered by flash light irradiation within a few seconds of process time had similar ionic conductivity to the electrolyte layer that was thermal sintered for about 10 h including cooling process.Coatings 2020, 10, 9 2 of 13 at low temperature. However, cerium oxide-based electrolytes have chemical instability due to a reduction of cerium ions from Ce 4+ to Ce 3+ when the electrochemical reaction occurs on the anode side in a high-temperature reduction environment. This reduction of cerium causes electronic conduction and results in loss of open-circuit voltage (OCV) of the SOFCs when it is used as an electrolyte by itself. In addition, it causes lattice expansion of the cerium oxide electrolyte on the fuel side, which leads to mechanical instability of the SOFC components [4,5]. To resolve these instability issues from ceria-based thin electrolyte layers and the relatively low ionic conductivity of YSZ, scandia-stabilized zirconia (ScSZ) was introduced. ScSZ is a zirconia-based oxide ion-conducting electrolyte material in which the dopant of YSZ is replaced with scandium, which is from the same family in the periodic table. The ionic radii of Zr 4+ is 0.84 Å, whereas the dopant ions are 0.87 Å for Sc 3+ and 0.94 Å for Y 3+ . Sc 3+ has an ionic radii similar to that of Zr 4+ , which reduces the steric-blocking effect during oxygen ion transport. Therefore, ScSZ has higher ionic conductivity than YSZ due to the ionic radii difference between the host (Zr 4+ ) and dopant ions (Y 3+ , Sc 3+ ). In addition, zirconia-based materials have superior chemical stability compared to ceria-based materials [6][7][8][9].Many deposition methods have been used to fabricate thin-film electrolyte layers for SOFCs, with an aim to minimize ionic transport resistance from the solid electrolyte. The methods can be generally categorized into two groups: vacuum processes and non-vacuum processes. The vacuum process deposition methods, such as physical vapor deposition (PVD) and chemical vapor deposition (CVD), allow for precise control of film microstruc...

A review on the preparation of anode materials and anode films for solid oxide fuel cell applications

“…In addition, volume shrinkage and cracking issues occur due to the imperfections of the material during the drying process 112,113 . The shrinkage issue tends to happen due to either the liquid (believed to be alcohol and water) or organic removal in the gel after the gelation process while the cracking issue is attributed to the drying process which involves the drying rate and thickness of the resultant gel 112,114,115 . Nevertheless, various methods and procedures are invented to increase the drying rate and changes of the gel density.…”

“…112,113 The shrinkage issue tends to happen due to either the liquid (believed to be alcohol and water) or organic removal in the gel after the gelation process while the cracking issue is attributed to the drying process which involves the drying rate and thickness of the resultant gel. 112,114,115 Nevertheless, various methods and procedures are invented to increase the drying rate and changes of the gel density. Rajaeiyan et al 47 revealed that the aluminum nanoparticles synthesized through sol-gel method shows low Brunauer-Emmett-Teller (BET) surface area compared with the sample produced using the co-precipitation method.…”

Infrared irradiation to drive phosphate condensation as a route to direct additive manufacturing of oxide ceramics

“…35,36 Smaller nanoparticles can also more efficiently pack a green body by filling voids between micro-sized particles. 37 Nominally, mixtures of 50 nm (99.5%, Sigma-Aldrich) and 100 nm (99.99%, MSE supplies) α-Al 2 O 3 powders as well as a 10 μm α-Al 2 O 3 powder (99.5%, Sigma-Aldrich) were used in this work (33 wt% of each). In addition, titanium dioxide (TiO 2 , anatase) was used as an additive since the incorporation of small amounts of TiO 2 (up to 5 wt%) into alumina has been shown to improve alumina densification at low temperatures (96% relative density obtained at 1450 • C with TiO 2 compared to 86.8% for undoped alumina).…”

Chemical Vapour Deposition of Scandia-Stabilised Zirconia Layers on Tubular Substrates at Low Temperatures

“…In contrast, Agarkov et al [ 23 ] consider that a regular solid solution can be obtained with a Sc 2 O 3 content in the range of 8–12 mol.%, while the monoclinic, tetragonal, tetragonal t’ and t”, and rhombohedral phases can exist with a molar dopant content of 5 to 12 mol.%. From the point of view of electrical properties, it is preferable if the electrolyte has a regular structure [ 3 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. However, at lower temperatures, i.e., below 650 °C, it is transformed into a rhombohedral phase with low ionic conductivity [ 24 , 25 , 26 ] and possibly a tetragonal one [ 17 , 26 ].…”

“…The ScSZ electrolyte is mainly obtained by powder sintering, which requires high temperatures, i.e., about 1400–1450 °C, e.g., [ 16 , 17 , 18 , 19 , 20 , 22 , 24 , 25 , 27 , 28 , 29 , 31 , 42 ]. There have also been studies on manufacturing of this electrolyte from slurries [ 13 , 42 ] and in the form of films using, e.g., the sol-gel method [ 21 , 33 ], chemical solution deposition (CSD) [ 35 ], atmospheric plasma spraying (APS) [ 36 ], and physical vapour deposition (PVD) methods [ 26 , 30 , 34 , 37 ]. In the case of obtaining electrolyte from suspensions, or using sol-gel or CSD methods, the material obtained had to be sintered at the final stage of the process at temperatures above 1000 °C in order to eliminate pores.…”