Microstructure of a Complex Oxide, Ho2MnxTa2−xO7(x≅ 1.0), with a Pyrochlore‐Related Structure

The ternary compound Ho2MnxTa2−xO7 was synthesized in air at 1523 K. Structural characterization of the compound was taken by X-ray diffractometry (XRD) and transmission electron microscopy (TEM). The compound possessed a trigonal super cell derived from a rhombohedral basic cell with the a/2 of the trigonal super cell. The super cell was caused by the ordering of Mn and Ta ions and the derived structure model was in agreement with that of the zirkelite structure with the space group P3121. The compound had stacking disorder with different stacking sequences along the c-axis. An orientation anomaly in the super cell reflections revealed that the super cell had an incommensurate nature.