Influence of B‐site cation in lattice dynamics of bilayered Ruddlesden–Popper Sr3B2O7 (B = Zr, Mo, Sn, Hf) compounds

Abstract

AbstractThe Raman and infrared (IR) wavenumbers for the Ruddlesden–Popper Srn + 1BnO3n + 1 (B = Zr, Mo, Sn, Hf) bilayered tetragonal compounds with n = 2 of symmetry and phase I4/mmm (Z = 2) have been analyzed with Wilson's GF matrix method. Theoretical assignments for the optical wavenumbers have been reported for the first time for the bilayered tetragonal Sr3Zr2O7, Sr3Mo2O7, Sr3Sn2O7, and Sr3Hf2O7 compounds in phase I4/mmm with the use of 10 short‐range force constants. Using the available data of the isostructural compounds Sr3Ti2O7, Sr3Mn2O7, and Sr3Fe2O7, we have tried to calculate the vibrational modes of the Sr3B2O7 (B = Zr, Mo, Sn, Hf) compounds in phase I4/mmm by the comparative method. Also, we have compared all these Sr3B2O7 (B = Zr, Mo, Sn, Hf) compounds together in terms of wavenumbers and force constants. The appropriate optical vibrational modes have been assigned to the bilayered tetragonal Sr3B2O7 (B = Zr, Mo, Sn, Hf) compounds in phase I4/mmm. The impact of cation‐B (B = Zr, Mo, Sn, Hf) exchange on the lattice dynamics of the tetragonal bilayered Sr3B2O7 (B = Zr, Mo, Sn, Hf) isostructural compounds has been analyzed by comparison of the zone center vibrational modes, force constants, and bond lengths. To understand the structure more clearly, an attempt is also made to analyze the effect of B‐cations on the affected apical bonds. It was observed that the B‐site substitutions have the least influence on the Sr layer and the equatorial bonds of octahedra; meanwhile, the outer apical bonds of the octahedra have shown the maximum impact. For each normal mode of the bilayered tetragonal Sr3B2O7 (B = Zr, Mo, Sn, Hf) Ruddlesden–Popper phase, the potential energy distribution (PED) has been analyzed for the noteworthy effects of short‐range force constants on calculated wavenumbers.