Sputtered lead scandium tantalate thin films: Pb⁴⁺ in B-sites in the perovskite structure

Perovskite lead scandium tantalate (PST) thin films have been prepared from lead rich targets by rf magnetron sputtering. Detailed microstructural chemical analysis of the films using transmission electron microscopy and energy dispersive X-ray spectroscopy techniques showed that they contained large amounts of excess lead and that this was located within the crystalline grains rather than solely at grain boundaries. It has been shown that the lattice parameters of the films are consistently larger than those for bulk PST. Comparison of the film lattice parameters with composition and with the lattice parameter/composition trend of a large number of lead containing perovskites strongly suggests that the excess lead is present on the B-sites of the structure as Pb⁴⁺.