Perovskite (ACuF3) to double perovskite (A3CuF6) (A = K, Rb) transformation by a simple shaking procedure with hydrogen peroxide

Abstract

Simple shaking of tetragonal perovskite structured KCuF3 with H2O2 resulted in its transformation to cryolite structure as verified from indexing all the diffracted peaks in the powder X-ray diffraction pattern in a cubic unit cell with a = 8.1253 (33) Å. Square morphology of the crystallites was noticed in FE-SEM image. The observed bands in FT-IR and Raman spectra could be finger printed to the positions reported for cubic cryolite structure. Elemental composition was confirmed by combining the results from inductively coupled plasma emission spectroscopy, X-ray photoelectron spectroscopy (XPS) and fluoride-ion selective electrode experiments. The existence of copper in +3 oxidation state in the sample has been confirmed from the observance of peaks with binding energies 932.2, 934.4, 951.6 and 954.4 eV in the core level XPS spectrum of Cu 2p3/2. Intense band at 223 and 280 nm followed by a broad band in the visible region in the UV–visible spectrum was noticed for K3CuF6 originating from ligand to metal charge transfer and d-d transitions of Cu3+, respectively. A similar transformation from RbCuF3 to cubic Rb3CuF6 was noticed. Use of K3CuF6 as catalyst for the photodegradation of aqueous rhodamine-6G dye solution has been demonstrated.