Brouwer Diagram Representation of Mixed Proton Conductivity

2 Brouwer Diagram Representation of Mixed Proton Conductivity 

A number of factors must be taken into account when the diagrammatic representation of mixed proton conductivity is attempted. The behavior of the solid depends upon the temperature, the dopant concentration, the partial pressure of oxygen, and the partial pressure of hydrogen or water vapor. Schematic representation of defect concentrations in mixed proton conductors on a Brouwer diagram therefore requires a four-dimensional depiction. A three-dimensional plot can be constructed if two variables, often temperature and dopant concentration, are fixed (Fig. 8.18a). It is often clearer to use two-dimensional sections of such a plot, constructed with three variables fixed (Fig. 8.18h-8.18 7). 

The Brouwer diagram approach can be illustrated with reference to the perovskite structure oxide system BaYbvPr VC 3, which has been explored as a potential cathode material for use in solid oxide fuel cells. The parent phase 

The vacancies can react with oxygen gas to generate holes  

The Pr4+ ion is easily reduced to Pr3+, which can be considered in terms of the electronic equilibrium  

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