Structural instability of EuTiO3from X-ray powder diffraction

We have recently predicted and subsequently verified experimentally by specific heat measurements that EuTiO3 undergoes a structural phase transition at elevated temperature T S = 282 K. The origin of the phase transition has been attributed to the softening of a transverse acoustic mode stemming from an oxygen octahedral rotation analogous to SrTiO3. Here we demonstrate that the theoretical interpretation is correct by using high-resolution laboratory X-ray powder diffraction which evidences a cubic to tetragonal phase transition in EuTiO3. The room temperature structure could be refined in with a = 3.9082(2) Å and at 100 K the refinement in the tetragonal space group resulted in a = 5.5192(2) and c = 7.8164(8) Å.