Non-porous Iron Titanate Thin Films Doped with Nitrogen: Optical, Structural, and Photocatalytic Properties

The synthesized undoped and nitrogen doped iron titanate films treated at 450 and 500 °C were crystallized forming pseudobrookite and landauite phase as shown by XRD patterns. The presence of urea in the synthesis procedure promoted the crystallization rate. XPS data indicated that iron ions existed in divalent and trivalent forms, and their ratio was changed for nitrogen-doped sample. The formation of the complexes between iron and urea during sol aging with the following reduction of Fe³⁺ to Fe²⁺ within calcination can be a reason not only for accumulation of iron onto the surface as shown by EDS but also for twice increase of divalent iron as registered by XPS. The iron titanate films extended the visible light absorption. Two band gap energy values for all iron-contained films were calculated. The photocatalytic response of all iron titanate films treated at 450 °C compared to pure titania films was spectacularly enhanced under UV and visible light. The slight enhance in photocatalytic activity of nitrogen-doped iron titanate films can be explained by the interstitial nitrogen incorporation rather than substitutional.