Lone-pair stabilized channels and blocked transport in apatite-related structures.

Two apatite-related silicates compounds, Tb2Pb3Si3O12 (I) and Pb5SiP2O12 (II), were obtained in the crystalline forms. Structure and ELF calculated results reveal that the lone pair cation of Pb2+ preferentially occupies the Cs site, and the repulsion between the mutual lone pair stabilizes channels. Moreover, combining conductivity results this preference has the important implications of exclusion and blocking the movement of the oxide ion in the channel of apatite-related structures. Our findings provide an experimental foundation for further interpreting the conductivity decrease in lone-pair ions as dopants into apatite-related silicate materials.