§ß^dq°÷¾j Ln 2 Mn x M 2|x O 7 (Lnrare earth or Y, MMo, Ta, Nb or W) m\¢ðÍ ìTǘ JåwHwdq°÷¾ºC5202194 åÃs£cå]¬ Ln 2 Mn x M 2|x O 7 (Lnrare earth or Y, MMo, Ta, Nb or W) was synthesized under ordinary pressure and various atmospheres with the expectation of achieving various symmetries and properties. These compounds are analyzed as similar structures of rhombohedrally distorted pyrochlore structures by Xray diraction (XRD). However, transmission electron microscope (TEM) images reveal dierences

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... een structures: MnTaO 7 possessed a trigonal structure with an incommesurate nature. The dierences in the structures were caused by the stacking sequence along the cdirection of a pair of A cation and B cation layers, where B cations formed a hexagonal tungsten bronze (HTB)type layer that is a characteristic framelayer in the pyrochlorerelated structure. In the case of Er 2 MnWO 7 , however, dierent types of structures with a trigonal cell show that no pair of Acation and Bcation layers existed along the cdirection in the crystal.