Synthesis, Structure, and Properties of Dion–Jacobson Double-Layered Perovskites A′SmNb2O7 (A′=Rb, K, Na, Li, H)

Dion-Jacobson-type layered perovskite compounds A′SmNb₂O₇ (A′=Rb, K, Na, Li, H) were synthesized using solid-state and ion-exchange methods. While the parent solid-state product RbSmNb₂O₇, has previously been studied, the ion-exchanged compounds were obtained and studied for the first time. The phase and chemical purity of the compounds were confirmed by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDX). The crystal structures of RbSmNb₂O₇ (I2 cm, a=0.54356(1) nm, b=0.53935(1) nm, c=2.1891(5) nm), KSmNb₂O₇ (I2 cm, a=0.53660(7) nm, b=0.54481(6) nm, c=2.1527(1) nm) and LiSmNb₂O₇ (B2 cm, a=0.54546(4) nm, b=0.53567(4) nm, c=2.04582(5) nm) were refined using the Rietveld method. Polyhedral distortions in these structures have been studied in detail. The thermal behavior of the compounds has been determined using differential thermal analysis (DTA), revealing that A′=Na, Li and H compounds are metastable hydrates, while A′=Rb and K compounds are stable. The optical band gap, valence band edge, and conduction band edge potentials of the compounds obtained were calculated using diffuse reflection spectroscopy data. A photocatalytic experiment was performed on the degradation of methylene blue under ultraviolet light. All of the samples obtained showed some asctivity in the reaction of dye photooxidation.