Steric Hindrance in Langbeinite-type K_2Cd_<2C>Mn_<2(1-c)>(SO_4)_3 Mixed Crystal(Condensed Matter : Structure, Mechanical and Thermal Properties)

概要

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To confirm the existence of the steric hindrance in the K_2B_2(SO_4)_3-type langbeinites, we study the annealing effect on the cubic crystal structure and the phase transition temperature of the K_2Cd_<2C>Mn_<2(1-c)>(SO_4)_3 mixed crystal of the nominal concentration c = 0.5. The annealing makes the considerably short atomic distances between the Cd/Mn and O atoms unchanged, while it reduces the real concentrations at the B-sites and decreases the phase transition temperature. These results are explained by the steric hindrance between the Cd/Mn ions and the surrounding SO_4 ions. We discuss that the phase transition of this mixed crystal as well as the K_2B_2(SO_4)_3-type pure langbeinites is driven by the steric hindrance.
2004-09-15