SOFC electrolytes

In order to create additional oxygen vacancy sites in the materials, the positively charged cation is substituted or doped by another cation with lower valence number. This leads to the creation of vacancies to achieve neutrality. For example, in YSZ, the oxygen vacancy Vf is created by replacing the zirconia cation Zr + with yttria cation Y +. This is explained by the defect equation written using the Kroger-Vink notation as 

A brief description of these electrolytes is given below  

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Shown in Figure 1.1 is the oxygen ion conductivity of selected oxides. Among these oxides, only a few materials have been developed as SOFC electrolytes due to numerous requirements of the electrolyte components. These requirements include fast ionic transport, negligible electronic conduction, and thermodynamic stability over a wide range of temperature and oxygen partial pressure. In addition, they must... 

Daun K.J., Beale S.B., Liu F., Smallwood G.J., 2006. Radiation heat transfer in planar SOFC electrolytes. Journal of Power Sources 157, 302-310. 

CHEMICAL SYNTHESIS OF MIXED OXIDE POWDERS FOR SOLID OXIDE FUEL CELL (SOFC) ELECTROLYTE AND ELECTRODES... 

A) Stabilized ZrOz. The Standard SOFC Electrolyte with a Large Electrolytic Domain... 

Maricle, D.L. et al.. Enhanced ceria a low-temperature SOFC electrolyte, Solid State Ionics, 52, 173-182 (1992). 

Proton-conducting ceramic membranes have been studied as SOFC electrolytes for intermediate temperature, around 800°C, and can also be used as electrolytes in steam electrolysis. The families of SrCeOj and BaCeOj with dopants such as Y, Yb, and Nd on the Ce site show good selectivity for proton transport. The advantage of... 

Solid-oxide fuel cells (SOFCs) are being developed for distributed power such as home power units and large power production units. They are not being considered for transportation, although that is conceivable with some difficulties. SOFC electrolytes are ceramic and operate at temperatures of up to 1,000°C, while PEM fuel... 

Figure 3.19 summarises data on conductivity of some materials considered for SOFC electrolytes, as a function of temperature (values along top, inverse temperatures along bottom abscissa). The uniform decline in conductivity at lower temperatures illustrates the compromise on efficiency associated with designing SOFCs to operate at lower temperatures. 

In both PEMFCs and SOFCs, there is a strong need to improve the electrolyte materials and to find substitutes for the traditional electrolytes, which are Nafion for the PEMFC and yttria-stabilized zirconia (YSZ) for the SOFC. In this paper, we will focus on the discussion of new developments in the field of SOFC electrolytes. For recent developments concerning other fuel cell types, the reader is referred to review articles and books. " ... 

PAFC electrolyte phosphoric acid MCFC electrolyte molten carbonate SOFC electrolyte solid oxide... 

Room temperature monoclinic zirconia has little use as a SOFC electrolyte because it is predominantly an electronic conductor with low oxygen ion conductivity [15]. Cubic zirconia has high ionic conductivity but needs to be stabilized so that it retains its cubic structure at room temperature. Nemst discovered and reported in 1899 that mixtures of zirconia with other oxides such as magnesia showed high ionic conduction at high temperatures [16]. Two years later, he patented his further observation that the material composition (15% yttria and 85% zirconia) was suitable for electric-lamp glowers [17]. Westinghouse Electric Corporation has used a similar zirconia-based electrolyte in their SOFC development since 1962 [18]. 

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