TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The evaporation-deposition step comprises: at least one first step of growth carried out with a deposition rate lower than or equal to a predetermined threshold, and at least one second step of growth carried out with a deposition rate greater than the threshold, where the threshold is 0.03 nm/second; at least two steps of growth, in which the deposition rate is constant, where the deposition rate increases from at least one step of growth to the next; or at least one step of growth, in which the deposition rate increases gradually, where, in each step of the growth, the deposition rate is maintained constant, or increases and optionally increases in a different manner in respective steps of growth. The method comprises selecting a necessary number of steps of growth as a function of the desired final thickness of the film of mixed oxide. In the method, for obtaining, on the substrate, a compact and homogeneous film of mixed oxide having a thickness of greater than 1.5 mu m, the evaporation-deposition step comprises at least four steps, preferably four steps of growth, in each of which the deposition rate is maintained constant for a predetermined time i.e. 60-90 minutes or 10-15 minutes, where: the deposition rate in each step of growth is greater than or equal to the deposition rate in the previous step of growth and lower than or equal to the deposition rate in the following step of growth, and the deposition rate increases between at least one step of growth and the next; and evaporation-deposition step comprises a first step of growth with a deposition rate constant at 0.01-0.03 nm/second, a second step of growth with a deposition rate constant at 0.01-0.03 nm/second or 0.2-0.4 nm/second, a third step of growth with a deposition rate constant at 0.04-0.06 nm/second or 0.7-1 nm/second, and a fourth step of growth with a deposition rate constant at 0.09-0.11 nm/second, or 1.6-2 nm/second. In the method, for obtaining on the substrate, a compact and homogeneous film of mixed oxide having a thickness of less than or equal to 1 mu m, the evaporation-deposition step comprises a first step and a second step of growth, in each of which the deposition rate is maintained constant for a predetermined time i.e. 60-90 minutes or 10-15 minutes, where the deposition rate is constant at 0.01-0.03 nm/second in the first step of growth, and is constant at 0.09-0.15 nm/second or 2-2.5 nm/second in the second step of growth The first step of growth is carried out with a deposition rate of not less than 0.01 nm/second or not less than 0.03 nm/second. The evaporation-deposition step comprises (between two successive steps of growth) re-establishment of the target, in which the target is supplied with mixed oxide. The method comprises an in situ heat treatment and annealing step of the film of mixed oxide, carried out in the same deposition chamber, in which the electron beam is sent onto the target for evaporating material that deposits on the substrate, and the film of mixed oxide deposited on the substrate in the evaporation-deposition step is heat treated and annealed in an inert at atmosphere or an oxidizing atmosphere. The in situ heat treatment and annealing step comprises: bringing the temperature of the pre-treated substrate 500-800 degrees C while introducing a gas flow into the deposition chamber, at least in the vicinity of the substrate, until reaching in the deposition chamber a partial pressure of 200-1000 mbar; and maintaining constant pressure and temperature in the deposition chamber 30-60 minutes. Preferred Components: The substrate is made of a composite material metal/oxide, oxide1/oxide2, or one of the latter already covered with an electrolytic layer for solid oxide fuel cells (SOFCs). The mixed oxide comprises: barium-cerium-yttrium oxide of formula (BaCe0.9Y0.1O3-d), or (BaCe0.8Y0.2O3-d); (lanthanum-strontium)-cobalt oxide of formula ((La0.8Sr0.2)0.95CoO3-d); yttrium oxide-zirconium oxide of formula ((Y2O3)0.08(ZrO2)0.92); gadolinium-cerium oxide of formula (Gd0.1Ce0.9O2-d) or (Gd0.2Ce0.8O2-d); samarium-cerium oxide of formula (Sm0.15Ce0.85O2-d) or (Sm0.2Ce0.85O2-d); scandium oxide-zirconium oxide ((Sc2O3)0.1(ZrO2)0.9); barium(cerium-zirconium)yttrium oxide of formula (Ba(CexZr1-x)0.9Y0.1O3-d); barium-indium-titanium-oxide of formula (Ba2In1.8Ti0.2O5+d) or (BaIn0.3Ti0.7O3-d); neodymium-nickel oxide of formula (Nd2NiO4+( delta ); praseodymium-nickel oxide of formula (Pr2NiO4+( delta ); erbium-bismuth oxide of formula (Er0.4Bi1.6O3); or dysprosium-tungsten-bismuth oxide of formula (Dy0.08W0.04Bi0.88O1.56) (where d, delta and x are not defined). The film of mixed oxide is an electrolytic or cathodic thin layer of a SOFC, and the substrate is a composite anodic substrate of the SOFC. EXAMPLE - Electron gun crucible was filled with 4 g of pellets of sintered material of 8mol.% yttrium stabilized zirconia ((Y2O3)0.08(ZrO2)0.92) (8-YSZ). Then nickel oxide/8-YSZ planar composite substrate with diameter of 80 mm and thickness of 0.3 mm was arranged in a deposition chamber, in which the pressure was brought to 2.0 x 10-5 mbar, and below a heating device arranged at a height of 25 cm above, the electron gun crucible. The deposition rate of 8-YSZ was kept under control by adjusting the power of the electron beam, in four steps of growth, where each step was performed for 90 minutes, and the deposition rate of first step was 0.02 nm/second, the second step was 0.02 nm/second, the third step was 0.1 nm/second, and the fourth step was 0.1 nm/second. During the first two steps of growth, no flow of gas was sent to the deposition chamber from the outside, and during the third and fourth step of growth, a flow of oxygen was sent, so that the pressure inside the deposition chamber was 10-4 mbar constant, where the temperature of the substrate was 700 degrees C, and the deposition time was 90 minutes/step. The obtained substrate was then subjected to heat treatment and annealing, in which substrate temperature was 700 degrees C, oxygen pressure was 500 mbar and the annealing time was 60 minutes.