Yttria stabilized zirconia electrical conductivity

The electrical conductivity of rare-earth oxide fluorides was first investigated for the development of a binary anion conductive solid electrolyte. As a result, it was found that the binary rare-earth oxide fluorides exhibited oxide ion conductivity. Among them, the conductivity of neodymium europium oxide fluoride, Nd2Eu203F6, was reported to be much higher than that of yttria-stabilized zirconia, YSZ, practically used as an oxygen sensor [34]. The electrical conductivities of the binary rare-earth oxide fluorides vary not only with the combination of Ln203 with Ln F3... 

G.Z. Cao, Electrical conductivity and oxygen semipermeability of terbia and yttria stabilized zirconia. /. Appl. Electrochem., 24 (1994) 1222-1224. 

Badwal, S.P.S., Electrical conductivity of single crystal and polycrystalline yttria-stabilized zirconia, J. Mater. Sci. 19 (1984) 1767-1776. 

Scandia Stabilized Zirconia (ScSZ) shows good potential for SOFC application because of its high electrical conductivity. But, the fundamental study such as suitable composition, mechanical properties and chemical stability are insufficient to compare with Yttria Stabilized Zirconia (YSZ) which is promising material for SOFC application. 

Electrolytes are distinguished from pure electronic conductors by the fact that the passage of an electric current is only insured by displacement of charged species called ions and hence accompanied by a transfer of matter. Therefore, electrolytes are entirely ionic electrical conductors without exhibiting any electronic conductivity (i.e., no free electrons). They can be found in the solid state (e.g., fluorite, beta-aluminas, yttria-stabilized zirconia, and silver iodide), liquid state (e.g., aqueous solutions, organic solvents, molten salts and ionic liquids), and gaseous state (e.g., ionized gases and plasmas). The ions (i.e., anions or cations)... 

Caz — which are not able to transport electric current. In the case of yttria-stabilized zirconia (YSZ), the substitution with 8 mol-% Y2O3 leads complete stabilization with the maximum conductivity and is preferred for most electrochemical applications. For that composition the following formula is obtained ... 

The electrochemical cell, as shown schematically in Fig. 1, consists of gas-tight ceramic electrolyse in the form of tubes, discs, planar substrates, or thick films which is sandwiched by precious metal like platinum or silver as electrodes. Both electrodes are in close contact with two separate gas compartments. Such cells often modified by other electrode materials like electric conducting oxides (chromites, manganites) are commonly used as gas sensors, fuel cells, and electrolysis cells. Yttria-stabilized zirconia (YSZ Zro.84To.i6< i.92) as oxide ionic conductor is widely used as an electrolyte. 

The major components of an individual SOFC cell include the electrolyte, the cathode, and the anode. Fuel cell stacks contain an electrical interconnect, which links individual cells together in series or parallel. The electrolyte is made from a ceramic such as yttria-stabilized zirconia (YSZ) and functions as a conductor of oxide ions. Oxygen atoms are reduced into oxide ions on the porous cathode surface by electrons, and then flow through the ceramic electrolyte to the fuel-rich porous anode where the oxide ions react with fuel (hydrogen), giving up electrons. The interconnect serves to conduct the electrons through an external circuit. 

Srdic V.V., Omoijan R.P. Electrical conductivity of sol-gel derived yttria-stabilized zirconia. Ceram. Int. 2001 27 859-863... 

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