Does BaTbO₃ Adopt the P1 Symmetry?

Abstract

A detailed profile analysis of X-ray diffraction data in the temperature range between 100 K and 723 K was carried out to settle a recent dispute on the symmetry and crystal structures of the perovskite BaTbO 3 . Through careful comparison of the Rietveld refinements, we found that there is no evidence to suggest a triclinic (P1) structure for BaTbO 3 . The cor- [a]

Response to “Does BaTbO3 Adopt the P1 Symmetry?”

“…We reply to the preceding correspondence “Does BaTbO 3 Adopt the P 1 Symmetry?” in this issue, in which the authors challenge the crystal structure of BaTbO 3– δ that has been re‐determined by us and published in this journal . Several points need more discussion.…”

“…The second point is the assertion that “A fundamental issue arises: which mechanism exists that may distort the aristotype cubic perovskite in such a way that metal ions are no longer equivalent?” . The discussions on the structure determination of BaBiO 3 presented by A. W. Sleight may answer this question.…”

“…The first point is the statement that “… the space group P 1 belongs to none of the space groups derived from the octahedral tilting”. However, in the papers cited in the correspondence by Fu and IJdo, the space group P 1 was indicated to be one of the space groups derived from the octahedral tilting. The space group P 1 is strongly related to P 1.…”

“…In the correspondence, one may read “Recognition of the remaining space groups can be done by examining the way of peak splitting of the basic ( h 00) and ( hhh )‐type reflections. In Table 1 (see ref …”

“…), the characteristics of these reflections in different space groups are summarized. Figure shows the room temperature X‐ray diffraction pattern of newly prepared BaTbO 3 with the insert showing the enlarged sections containing the basic (200) (2 θ ≈ 42.2°) and (222) (2 θ ≈ 77.2°) reflections.” The index ( hkl ) is discussed in the aristotype cubic cell with a ≈ 4.2 Å. In order to avoid misunderstanding, we like to use the index in its own space group with proper lattice parameters.…”