Abstract:
The KNb3O8 triniobate potassium (Amam (63), a = 8.903 Å, b = 21.160 Å, c = 3.799 Å) and the K4Nb6O17 (P21nb (33); a = 7.83 Å, b = 33.2 Å, c = 6.46 Å) phases are both layered compounds that show excellent photocatalytic activity for degradation of organic contaminants in water, CO2 and hazardous microorganisms and intercalation properties together with electrochemical performances that are attractive as anode active materials for sodium-ion battery. In this study, we report the first synthesis of KNb3O8 niobate in thin film form, and the first growth of the phase K4Nb6O17 with epitaxial relationships with the substrate. The films were prepared by pulsed laser deposition on (100)SrTiO3 (STO) and characterized by X-ray diffraction, scanning and transmission electron microscopy, and X-ray energy dispersive spectroscopy. The KNb3O8 films, made of elongated crystals (500 nm long and 50-75 nm wide), with the [100] direction parallel to the elongation direction, are well-crystallized. They are (010)-preferentially oriented and present epitaxial relationships with the substrate, namely (010)KNb3O8 // (100)STO, [100] KNb3O8 // [010]STO and [001]KNb3O8 // [001]STO. The KNb2.66O7.73 composition with a very narrow range is measured, slight potassium amount changes leading to the growth of other niobates (as K3Nb6O19 and K4Nb6O17). The K4Nb6O17 films grow as rectangular lamellas of several microns with the following relationships with the substrate: (010) K4Nb6O17 // (100) STO, [100] K4Nb6O17 // [010] STO, [001] K4Nb6O17 // [001] STO. In both compound films, Sn was intercalated in order to reduce the bandgap of the niobates.
|
