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Abstract:
We present a (re)investigation of the hexaoxometalates Li8MO6 (M = Sn,
Pb, Zr, Hf) and Li7MO6 (M = Nb, Ta, Sb, Bi). Lithium motion and ionic
conductivity in the hexaoxometalates were studied using impedance
spectroscopy (for Li7MO6, M = Sb, Bi, Ta) and Li-6 and Li-7 solid-state
nuclear magnetic resonance (for Li7TaO6). The NMR data indicate a
considerable exchange of Li among the tetrahedral and octahedral voids
even at ambient temperature. In an investigation of the crystal
structures using laboratory and synchrotron X-ray powder diffraction
techniques, the structures of Li7TaO6, Li7NbO6, and Li7SbO6 could be
solved and refined. All three reveal a triclinic metric (Li7SbO6,
triclinic, P (1) over bar, a = 5.38503(6) Angstrom, b = 5.89164(7)
Angstrom, c = 5.43074(6) Angstrom, alpha = 117.2210(6)degrees, beta =
119.6311(6)0, gamma = 63.2520(7)degrees, V = 127.454(3) Angstrom(3), Z
= 1; Li7NbO6, triclinic, P (1) over bar, a = 5.37932(9) Angstrom, b =
5.91942(11) Angstrom, c = 5.37922(9) Angstrom, alpha = 117.0033(9)-,
beta = 119.6023(7)degrees, gamma = 63.2570(9)degrees, V = 126.938(4)
Angstrom(3), Z = 1; Li7TaO6, triclinic, P (1) over bar, a = 5.38486(2)
Angstrom, b = 5.92014(3) Angstrom, c = 5.38551(2) Angstrom, alpha =
117.0108(2)degrees, beta = 119.6132(2)degrees, gamma =
63,2492(2)degrees, V = 127.208(1) Angstrom(3), Z = 1.
