## 3 Results  
The electrical characteristics of multicomponent films are determined by the crystal structure of the material, the component and phase composition, the size of the crystallites, the presence of impurity phases and deformations of the crystal lattice. These factors significantly affect the dielectric permittivity of FE films, as well as the nonlinearity, losses and performance of devices based on them. For the development of ferroelectric microwave devices, it is important to understand the relationship between the structural and electrical properties of films and the technological conditions of their formation. The results of recent studies indicate a significantly different effect of the composition of the gas medium in which the formation of FE film occurs on their structural properties and phase composition. Thus, the perovskite crystal structure of barium-strontium titanate without secondary phases is confidently formed in a purely oxygen medium on sapphire, silicon carbide, magnesium oxide, etc. On the other hand, it is noted in [34,38] that attempts to form FE film with substitution of Ti by Zr or Sn atoms on dielectric substrates in an oxygen-rich gas medium lead to the formation of a multiphase structure consisting of purely dielectric barium zirconates or barium stannates and secondary phases with a high content of titanium--simple oxides and barium polytitanates (BaTi\({}_{2}\)O\({}_{5}\), BaTi\({}_{5}\)O\({}_{11}\), etc.). This can be explained by the kinetics of Ti oxidation in a medium with a high oxygen content, when the rate of formation of secondary phases of titanium significantly exceeds the rate of formation of ferroelectric BaTiO\({}_{3}\). In this case, the absence of free Ti on the substrate surface may cause the formation of pure barium zirconates/stannates. The situation is complicated by the fact that many titanates have a similar crystal structure [39, 40, 41], which often leads to the overlap of diffraction reflections from different phases and complicates their identification. Each of these compounds has its own permittivity \(\varepsilon\) and the dependence \(\varepsilon\) (T), which can affect the electrophysical properties of the ferroelectric device as a whole. It follows that for the formation of single-phase films of barium titanate-stannate on dielectric substrates by deposition from the gas phase, the oxygen content in the working gas should not exceed 50%. Figure 1 shows the diffractograms of BTS films deposited on alumina at a substrate temperature of \(T_{s}=650\)\({}^{\circ}\)C and at different concentrations of oxygen in the working gas. At the angles \(32^{\circ},39^{\circ},45^{\circ},55^{\circ}\), the dotted lines on the left correspond to the positions of the reflexes for pure barium stannate, the lines on the right correspond to the barium titanate, the reflexes from the substrate are marked with diamonds (PDF 46-1212). Three factors draw attention to themselves. (i) In pure argon, the structure of perovskite is practically not formed. (ii) For films deposited in a medium containing 40% oxygen in a gas mixture, the positions of the reflexes correspond to BaSnO\({}_{3}\) with the lattice parameter 4.12 A, without signs of the presence of a solid solution. The probable cause of the formation of the dielectric barium stannate may be the presence of impurity phases of titanium oxides on the substrate, the possible positions of XRD reflexes from which are marked in Figure 1 with red and blue dotted lines (PDF 21-1272 TiO\({}_{2}\) Anatase; PDF 8-117 TiO; PDF 29-1360 TiO\({}_{2}\) Brookite; PDF 34-133 BaTi\({}_{2}\)O\({}_{5}\)), similar to [34,38]. (iii) The reflexes from the BTS phase in Figure 1 are significantly shifted towards large angles when the oxygen content in the gas medium decreases from 40 to 20%, that for polycrystalline samples means a change in the composition of the solid solution (the ratio of Ti and Sn) according to the Vegard's law (see the inset in Figure 1) [42].