The Aurivillius phase structure is highly anisotropic, and the films show strongly-preferred caxis orientation, as is evidenced by the majority of XRD peaks displaying (00l) reflections. TEM images (Fig. ) of samples from Series 1 confirm the layered m = 5 structure and verify the preferential growth of grains in directions normal to the stacking axis (c-axis) of the layers. The grains crystallize with plate-like morphology with in-plane grain size ranging from 10 nm to 2 μm (Fig. ). The crystallites overlap one another at grain boundaries (Fig. ), meaning that thickness variation (typically 89 nm ± 33 nm) is observed across the samples, with RMS roughness ranging from 16 to 27 nm.