Interstitial dopants

Powder XR diffraction spectra confirm that all materials are single phase solid solutions with a cubic fluorite structure. Even when 10 mol% of the cations is substituted with dopant the original structure is retained. We used Kim s formula (28) and the corresponding ion radii (29) to estimate the concentration of dopant in the cerium oxide lattice. The calculated lattice parameters show that less dopant is present in the bulk than expected. As no other phases are present in the spectrum, we expect dopant-enriched crystal surfaces, and possibly some interstitial dopant cations. However, this kind of surface enrichment cannot be determined by XR diffraction owing to the lower ordering at the surface. 

Consulting a Periodic Table and Table of Atomic Radii, what atoms would be suitable (a) interstitial dopants and (b) substimtional dopants within a Mn lattice Show your calculations and rationale. 

As seen earlier, the steps used to purify iron involves carbonaceous material to remove the oxide-based impurities, through exothermic formation of CO and CO2. Hence, carbon will be pervasive in a variety of concentrations throughout all phases of iron and steels, present as an interstitial dopant within these lattices. Experimental evidence shows that carbon-doped iron polymorphs are indeed interstitial solid solutions. For instance, the carbon atoms in bcc ferrite are located only on empty face-centered positions. However, very few of these positions are occupied throughout the lattice, as the maximum solubility of carbon in a-Fe is only between 0.01 and 0.02 wt%. From a metallic-bonding standpoint, the addition of carbon in the lattice acts as an electron sink, that is able to accept some of the delocalized electron... 

What is the difference between substitutional and interstitial dopants Provide examples for each type. 

The role of anisotropy and interchain interaction has been identified through dc and ac conductivity of stretch films, Kramers-Kronig analysis of reflectance on stretched films, anisotropic microwave frequency conductivity [44,52] and muon spin relaxation [62]. The role of interaction of spin of interstitial dopants with the conduction electrons at low temperatures has recently been explored by Y.W. Park and coworkers [63]. 

Interstitial dopants Dissolved atoms or ions in interstitial sites of the host lattice 0... 

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