Strontium ionic crystal radius

Most trace elements have values of D< C 1, simply because they differ substantially either in ionic radius or ionic charge, or both, from the atoms of the major elements they replace in the crystal lattice. Because of this, they are called incompatible. Exceptions are trace elements such as strontium in plagioclase, ytterbium, lutetium, and scandium in garnet, nickel in olivine, and scandium in clinopyroxene. These latter elements acmally fit into their host crystal structures slightly better than the major elements they replace, and they are therefore called compatible. Thus, most chemical elements of the periodic table are trace elements, and most of them are incompatible only a handful are compatible. 

Calcium, strontium and barium each have slightly different impacts on the properties of the perovskite. This is due, in part, to the difference in ionic radii of the ions. Calcium has a radius of 1.36 A, whereas the radii of strontium and barium are 1.44 and 1.65, respectively. Thus barium-containing perovskites have a more open crystal lattice and thus have a higher ionic conductivity compared to strontium- and calcium-based materials. However, barium is more reactive towards C02-containing gas mixtures and forms barium carbonate very readily. 

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