Does BaTbO3 Adopt the P1 Symmetry?

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 BaTbO3. Through careful comparison of the Rietveld refinements, we found that there is no evidence to suggest a triclinic (P1) structure for BaTbO3. The correct space groups with decreasing temperature are I4/mcm and Imma, respectively. At around room temperature both structures co‐exist. The phase sequence of “Pm3m” → I4/mcm → Imma is just the one expected to occur in A(II)B(IV)O3‐type perovskites. The recently published structure of the perovskite BaTiO3 was reinvestigated in the temperature range between 100 K and 723 K. As alternative to the space group P1, with decreasing temperature the space groups I4/mcm and Imma are proposed.