To determine the coating thickness, a cross-section of the coated plates was prepared and then examined under an optical microscope. It was observed that thicker coatings were more inhomogeneous and brittle, more prone to delamination or flaking off. Based on these observations, only samples with up to three subsequent coating steps were prepared. The coating thicknesses were 2.9, 4.0 and 5.3 µm for one, two and three coatings, respectively. As can be seen in Figure , the coating thicknesses are very homogeneous, which is a result of the pre-dispersion via ball milling. Raman spectroscopy was employed to evaluate the phase composition and crystallinity of the coatings (see Figure ), since the small thickness is challenging for metallographic cross-section examination. Three main peaks are observable for the samples at Raman frequencies of 397, 517 and 639 cm -1 , which correspond to anatase TiO2. This is expected as the employed P25 predominantly comprises anatase, the smaller feature at about 440-450 cm -1 also indicates the presence of the expected minority phase, rutile.