Thin Film Electrolytes: Yttria Stabilized Zirconia and Ceria (original) (raw)
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Fabrication and Characterization of YSZ-Coated Ceria Electrolytes
ECS Proceedings Volumes, 1993
Doped ceria electrolytes were fabricated by pressureless sintering powder compacts. Thin (~2 pm) layer o f yttria-stabilized zirconia (YSZ) was deposited by sputtering over the sintered discs. Heating to 900°C led to cracking of the YSZ films. H owever, thermal treatm ent at 1500°C improved the quality of the film by crack healing. On some of discs, a film of YSZ was deposited by electrochemical vapor deposition (EVD). It was shown that YSZ films do not delaminate. Open circuit voltage (OCV) was measured across the discs, with hydrogen fuel on one side and oxygen on the other, by exposing the YSZ-coated side to fuel as well as oxygen. It is shown that the OCV is higher if the coated side is exposed to oxygen. The underlying rationale is discussed.
Ohmic resistance of thin yttria stabilized zirconia film and electrode–electrolyte contact area
Materials Science and Engineering: B, 2001
This paper describes the factors influencing the measured value of ohmic resistance together with the structural and optical characterization of two thin yttria stabilized zirconia films. The investigated films were deposited on n-doped Si (1 1 1) substrates using e-beam evaporation of (YO 1.5 ) 0.18 (ZrO 2 ) 0.82 pellets at 150°C. The crystallographic structures of both films were found as amorphous (thickness of 240 nm) and polycrystalline (thickness of 330 nm) with the grain size 36 nm. The imperfection of the electrical contact, in the case of thin films the thicknesses of which are 100 nm, can dramatically influence the magnitude of measured ohmic resistance. Moreover, the ratio of R eff /R true cannot be determined from measurements of films with various thicknesses, but only estimated from micrographs or from measurements of films of the material with the known electrical conductivity. The different behaviour of the refractive index and the extinction coefficient of the two investigated films can be attributed to different crystallographic structures of the films.
Preparation of thin yttria-stabilized zirconia films by vapor-phase electrolytic deposition
Solid State Ionics, 1992
Yttria-stabilized zirconia (YSZ) thin films were prepared by vapor-phase-electrolytic deposition (VED) at the temperature of 1100°C under reduced pressure using ZrC14, YCl, and Hz0 gases as source materials. Porous calcia-stabilized zirconia was used as a substrate to prepare thin YSZ film. The deposition rate of VED process was 7 pm hh' which was about four times faster than that of CVD-EVD process under the same conditions. The YSZ thin film prepared by VED process was pinhole-free and its ionic conductivity was nearly equal to that of the sintered YSZ.
Journal of Materials Science: Materials in Electronics, 2018
The physical, chemical, and electrical characteristics of intercalated nano-layers of Y 2 O 3 and ZrO 2 , sequentially deposited by sputtering and thermal atomic-layer deposition (ALD), are reported in order to assess their use as electronic and/or ionic conductor. In general, the physical and chemical properties of sputtered and ALD-YSZ show good characteristics while a relatively high dielectric constant of about 30, along with a large capacitance-voltage hysteresis, are obtained for ALD-YSZ. Additionally, using inert or reactive metals as gate electrodes on YSZ/n-Si structures, promotes a change in the conduction of electronic and ionic species of YSZ and their influence is also reported.
Russian Journal of Electrochemistry, 2010
The surface of ceramic electrolyte ZrO 2 + 9 mol % Y 2 O 3 , hereinafter referred to as YSZ (abbrevi ated yttria stabilized zirconia), was modified with 0.1 to 0.2 mcm oxide films of ZrO 2 , Y 2 O 3 , and YSZ (same composition as substrate) by immersion in alcohol solutions of the relevant salts and further annealing. The results of scanning electronic microscopy and X ray power diffraction evidence epitaxial film growth. By means of impedance spectroscopy at the temperatures of 500 to 600°C, the effect of YZS electrolyte surface modification with ZrO 2 , Y 2 O 3 , and YSZ films to the polarization resistance of silver electrode was studied.
Effect of ion implantation doping on electrical properties of yttria-stabilized zirconia thin films
Solid State Ionics, 1992
The change in conductivity of Fe and Ti implanted if-sputtered layers of yttria-stabilized zirconia (YSZ) was studied as a function of the temperature (400-800 °C) and oxygen partial pressure. In an oxidized state and in the temperature range of 400-600 ° C, the conductivity of the Fe implanted YSZ film ( 15 keV, 8 × 10 '6 at.cm -2) was dominated by the n-type electronic conductivity of a thin Fe203 layer with an estimated thickness of less than 2 nm on top of the YSZ thin film. Due to the incorporation of a part of the implanted Fe atoms in the yttria-stabilized zirconia lattice, the ionic conductivity was somewhat decreased. In a reducing atmosphere this electronic conduction was no longer observed. In an oxidized state, the conductivity of the YSZ film was not influenced by the implantation of Ti ( 15 keV, 8 X 1016 at.cm-2). After reduction in a H2 atmosphere, an increase in the conductivity of the sputtered film with 2-3 orders of magnitude was observed. This has been ascribed to the presence of nonstoichiometric TiO2_x, which is an n-type semiconductor.
Journal of Power Sources, 2011
Si-diffusion from Si-based substrates into yttria-stabilized-zirconia (YSZ) thin films and its impact on their microstructure and chemistry is investigated. YSZ thin films used in electrochemical applications based on micro-electrochemical systems (MEMS) are deposited via spray pyrolysis onto silicon-based and silicon-free substrates, i.e. Si x N y -coated Si wafer, SiO 2 single crystals and Al 2 O 3 , sapphire. The samples are annealed at 600 • C and 1000 • C for 20 h in air. Transmission electron microscopy (TEM) showed that the Si x N y -coated Si wafer is oxidized to SiO z at the interface to the YSZ thin film at temperatures as low as 600 • C. On all YSZ thin films, silica is detected by X-ray photoelectron spectroscopy (XPS). A particular large Si concentration of up to 11 at% is detected at the surface of the YSZ thin films when deposited on silicon-based substrates after annealing at 1000 • C. Their grain boundary mobility is reduced 2.5 times due to the incorporation of SiO 2 . YSZ films on Si-based substrates annealed at 600 • C show a grain size gradient from the interface to the surface of 3 nm to 10 nm. For these films, the silicon content is about 1.5 at% at the thin film's surface.
Grain-Size Effects in YSZ Thin-Film Electrolytes
Journal of The American Ceramic Society, 2009
The transport properties of oxygen-ion conducting yttria-stabilized zirconia (YSZ)—featuring mean grain sizes from a few nm up to the μm regime—were studied with regard to grain-size effects. Chemically homogeneous, 8.3 mol% YSZ thin films (thickness approximately 400 nm) were processed on single-crystal sapphire substrates by a sol–gel method. The mean grain size d of the thin films was systematically adjusted to 5 nm≤d≤782 nm by (i) a rapid thermal annealing step for conversion into the oxide phase and (ii) a consecutive calcination step at 650°C≤Tcal (24 h) ≤1400°C for grain growth. The quality of the thin films was examined with respect to chemical homogeneity, crystal structure, grain-size, and grain-boundary properties. Total and specific conductivities of the thin films were characterized by means of electrical impedance spectroscopy at 200°≤T≤400°C in ambient air, where a complex nonlinear least-squares approximation was applied to determine the bulk conductivity and the grain-boundary conductivity. Despite grain boundaries being free of second phases, oxygen transport was observed to be impeded by the grain boundaries as the specific grain-boundary conductivity was determined to be two orders of magnitude below the bulk conductivity for thin films with d>36 nm. The transport properties of nanoscaled YSZ thin films (5 nm≤d≤36 nm) were modeled by application of the brick-layer model indicating the absence of beneficial grain-size effects at the nanoscale.