At high temperature, La 2 Mo 2 O 9 has a structure closely related to cubic -SnWO 4 , which contains WO 4 tetrahedra and

At high temperature, La₂Mo₂O₉ has a structure closely related to cubic β-SnWO₄, which contains WO₄ tetrahedra and Sn in a distorted six-coordinate environment. On cooling through 580 °C, a 2a × 3b × 4c monoclinic superstructure is formed. Correlate these observations with the conductivity data in Figure 13.18, and suggest a mechanism for conductivity above 580 °C.

Figure 13.18

log(o) (S/cm) -1 -2 -3 -4 -5 -6 0.7 900 700 coo temperature (C) 500 1.0 BiE403 Bain0 BizVosCuo.105.35 300 YoosZra.9201.96 1.3 1000/T (K-) 1.6 a = 10- S/cm LaMoOg booo Big.913V0.08701.587 1.9