Structural study of the complex perovskite Ba4(Ba2Nb2)O11

Structural investigations of single crystals of the complex perovskite Ba4(Ba2Nb2)O11 synthesized by the cold crucible induction melting method were carried out in the present study. The material was studied in the as prepared, dry and hydrated states. In dry and as prepared state, based on the observations both in TEM and XRD, a body centered tetragonal (BCT) structure having the space group I4/mmm (no. 80) and cell dimensions a ≈ 8.75 Å and c ≈ 17.1 Å was proposed. In hydrated state a hexagonal structure having the space group P6¯m2 (no. 187) and cell dimensions a = 6.038 Å and c = 18.0383 Å was proposed. Contrary to previous observations, this sample showed considerable water uptake when compared to sample with the same composition prepared by solid state reaction technique. The thermogravimetric (TG) curve also indicated a phase transition during water uptake.