Zirconia electrolyte films

Zhang, Y. et. al., A study of the process parameters for yttria-stabilized zirconia electrolyte films preparcd by screen-printing, J. Power Sources 160 (2006) 1065-1073. 

Basu, R.N., Randall, C. A, and Mayo, M.J. (2001), Fabrication of dense zirconia electrolyte films for tubular solid oxide fuel cells by electrophoretic deposition, J. Am. Ceram. Soc. 84, 33-40. 

The experimental apparatus has been described in detail elsewhere (11,12,22). In previous communications we have also described the porous silver catalyst film deposition and characterization procedure (11,12). Ten different reactor-cells were used in the present investigation. The cells differed in the silver catalyst surface area as shown in Table I. Catalysts 2 through 5 had been also used in a previous study (17). The reactor-cells also differed in the zirconia electrolyte thickness which could not be measured accurately. The electrolyte thickness varies roughly between 150 and 300 ym. 

T) A more compact thick film zirconia oxygen sensor with a built-in heater has been developed. In this sensor, the reference oxygen gas is not air the oxygen gas is generated electrolytically at the interface between the reference electrode and the porous zirconia electrolyte. 

Considering the obtained experimental data, it is possible to propose a model of the formation of a porous structure of the films of zirconia-based solid electrolytes. The model assumes the formation of pores and submicropores when vacancies, which are trapped during sputtering of the solid-electrolyte films (the sputtering temperature was Tf < 0.3Tmeit), pass to sinks and then condense [2,3,4,5], The sinks are boundaries between the crystallites forming the film structure. 

The simultaneous analysis of the results of the study into the structure and the formation of the solid-electrolyte films led to the following conclusion the nanocrystalline structure of the solid-electrolyte films at the initial stage of their formation caused the appearance of a columnar structure of the films of the zirconia-based solid electrolyte during their sputtering. 

Electrochemical vapor deposition has been explored for making gas-tight, dense, solid electrolyte films on porous substrates, - and the most smdied system has been the yttria-stabilized zirconia films on porous alumina substrates for solid... 

Doped zirconia and ceria 1-10 pm thick electrolyte films... 

The electrolyte film can be fabricated by a number of processes depending upon the configuration of the cells. For tubular SOFCs, an electrochemical vapour deposition (EVD) technique was developed by Westinghouse Electric Corporation (now Siemens Westinghouse Power Corporation) in 1977 [40] to fabricate gas-tight thin layers of doped zirconia. This EVD process involved growing a dense oxide layer on a porous substrate at elevated temperatures and reduced pressures, as described in Figure 4.12 [41]. 

Empirical development of the nickel-zirconia anode over several decades has led to solid oxide fuel cells with adequate service life and performance, but fuel reforming is still required to operate with commercially available hydrocarbon fuels. It has become evident that the anode reactions are dominated by the three-phase boundary and that the microstructure of the composite cermet anodes is pivotal. Consequently, the processing methods used for making the anode powders, and the fabrication techniques used for deposition on the electrolyte are critical in making high performance anodes. Anode-supported cells with very thin electrolyte films are becoming interesting for operation at lower temperatures. 

Fig. 10 Anode-supported thin film zirconia electrolyte support. Electrolyte film was co-fired along with anode functional layer (AFL) coated anode support and combination of the processing technique )delded a current density ( 1 A cm at 0.7) at 800°C (Basu et al. 2005).

Ding J, Liu J (2008) An anode-supported solid oxide fuel cell with spray-coated yttria-stabilized zirconia (YSZ) electrolyte film. Solid State Ion 179 1246-1249... 

Y.-Y. Chen, W.-C.J Wei, Processing and characterization of ultra-thin yttria-stabilized zirconia (YSZ) electrolytic films for SOFC. Solid State Ionics 177(3 ), 351-357 (2006)... 

An anode supported type SOFC was recently proposed as a design which can operate at lower temperatures <900 °C. An extremely high power density, over 1 W/cm, was reported for a single cell by Visco et al. (1999) at Lawrence Berkeley National Laboratory, and University of California in US, and now the stack developments are promoted by Pacific Northwest National Laboratoiy (PNNL) and Delphi Co. for auxiliary power unit in heavy duty mobiles (Mukeqee et al., 2003). In an anode supported SOFC, a thin, dense electrolyte film (thickness 10 (um) is prepared on a porous composite substrate of nickel metal and yttria stabilized zirconia (YSZ) as the anode, and the porous cathode is attached to the dense electrolyte. The thin electrolyte and planar cell stack decreases the Ohmic loss, and results in a high power... 

The tape-casting method makes possible the fabrication of films in the region of several hundred micrometers thick. The mechanical strength allows the use of such a solid electrolyte as the structural element for devices such as the high-temperature solid oxide fuel cell in which zirconia-based solid electrolytes are employed both as electrolyte and as mechanical separator of the electrodes. 

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