## Abstract

The quasibinary system KBi_{2-x}Pb_{x} has been investigated, both experimentally and theoretically. Phases with compositions 0 ≤ x ≤ 1.2 were synthesized and structurally characterized by X-ray diffraction experiments. For low values of x (0 ≤ x < 0.6), KBi _{2-x}Pb_{x} adopts the cubic Laves-phase structure MgCu _{2} (space group Fd3m), which contains a rigid framework of corner-condensed symmetry-equivalent tetrahedra formed by randomly distributed Bi and Pb atoms. For compositions x ≥ 0.6, these tetrahedra become alternately elongated and contracted. The distortion of the framework lowers the space-group symmetry to F43m (KBi_{1.2}Pb_{0.8}, F43m, Z = 8, a = 9.572(1) Å). Magnetometer measurements show that KBi_{2} (x = 0) is metallic and goes through a superconducting transition below 3.5 K. First principles calculations reveal that the Fd3m → F43m distortion is largest for KBiPb (x = 1.0), which at the same time turns into a semiconductor. Thus, F43m KBiPb corresponds to a proper charge-balanced Zintl phase, K ^{+}[BiPb]^{-}, with separated polyanionic tetrahedra, (Bi _{2}Pb_{2})^{2-}. However, it was not possible to prepare F43m KBiPb. Syntheses attempting to increase the Pb content in KBi _{2-x}Pb_{x} above x = 0.8 yielded additional, not yet characterized, ternary phases.

Original language | English |
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Pages (from-to) | 7423-7430 |

Number of pages | 8 |

Journal | Inorganic Chemistry |

Volume | 44 |

Issue number | 21 |

DOIs | |

State | Published - 17 Oct 2005 |

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