Superstructures homogeneous systems

The ternary iron oxides, as exemplified by the iron-niobium system, offer an opportunity to obtain single-phase, conducting n-type iron oxides in which the conductivity can be controlled by means of chemical substitution. At first glance, FeNbO and FeNb Og might appear to be very different materials. Yet as MM O and MM Og they merely represent superstructures of the basic a-PbO. structure obtained under the conditions of preparation (7 ). Consequently, they form a solid solution in which the two valence states of iron are uniformly distributed throughout a single homogeneous phase (j3). 

The building block of the superstructure representation is the generic reactor unit, which follows the shadow reactor concept (32). This generic unit is illustrated in Figure 4. Each generic unit consists of reactor compartments in each phase of the system, and each processes the reaction. The shadow reactor compartment assumes a state from the set of homogeneous reactors. The default units in the set include CSTRs and PFRs with side streams. The interface between a given pair of... 

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