A reinvestigation of Sillén X1-type lead tellurium oxyhalides, Pb3TeO4X2 (X = Cl, Br, I)

The oxyhalides Pb3TeO4X2 (X=ClX=Cl, Br, I) have been prepared from Pb3O2X2 and TeO2. All three compounds are isostructural and adopt the Nd2O2Te (PbBiO2I) structure type (I4/mI4/m, Z=1Z=1) according to single-crystal and powder X-ray and electron diffraction data. Contrary to previous results, the Pb/Te cation ordering was found to be nearly the same as Pb/I in schwartzembergite, Pb5IO4(OH)2Cl3 but not Pb/Sb in nadorite PbSbO2Cl. We discuss the factors affecting Pb/M cation ordering in layered (Sillén-type) multinary oxyhalides of lead.

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