In this work, we present the stoichiometric behaviour of Ba 2+ and Sr 2+ when they are deposited to make a solid solution of barium strontium titanate. Ba x Sr 1−x TiO 3 (BST) thin films of nanometric order on a quartz substrate were obtained by means of in-situ RF-magnetron co-sputtering at 495 • C temperature, applying a total power of 120 W divided into intervals of 15 W that was distributed between two magnetron sputtering cathodes containing targets of BaTiO 3 and SrTiO 3 , as follows: 0-120, 15-105, 30-90, 45-75, 60-60, 75-45, 90-30, 105-15 and 120-0 W. Boltzmann's sigmoidal modified equation (Boltzmann's profile) is proposed to explain the behaviour and the deposition ratio Ba/Sr of the BST as a function of the RF-magnetron power. The Boltzmann's profile proposal shows concordance with experimental data of deposits of BST on substrates of nichrome under the same experimental conditions, showing differences in the ratio Ba/Sr of the BST due to the influence of the substrate.

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Semicontinuous heterophase polymerization was used to copolymerize methyl methacrylate (MMA) with reactive surfactant HITENOL BC10 (HBC10) at 60°C using sodium dodecyl sulfate as pre-stabilizing agent and potassium persulfate as initiator. The mixture of MMA and HBC10 was added at constant rate in continuous mode varying the MMA/HBC10 ratio. High-polymerization rates were observed, decreasing as the MMA/HBC10 ratio decreased. Latexes with polymer content near 20% and polymer to surfactant (P/S) weight ratios between 5 and 15 were obtained. Particle sizes distribution were bimodal in all cases with a tendency to be monomodal as HBC10 concentration increased which was ascribed to enhanced particle stabilization by the presence of HBC10. The average particle diameters at the end of polymerizations for the first and second populations were around 10 and 50 nm, respectively. Very high average molecular weights were observed (1.4 9 10 6 B M w B 2.1 9 10 6 g/mol), which decreased when HBC10 concentration increased. The corresponding polydispersity indexes (M w /M n ) were in the range of 1.45-2.24.

A novel procedure based on the use of the Boltzmann equation to model the parameter, the film deposition rate, and the optical band gap of Ba x Sr 1−x TiO 3 thin films is proposed. The Ba x Sr 1−x TiO 3 films were prepared by RF cosputtering from BaTiO 3 and SrTiO 3 targets changing the power applied to each magnetron to obtain different Ba/Sr contents. The method to calculate consisted of fitting the angular shift of (110), (111), and (211) diffraction peaks observed as the density of substitutional Ba 2+ increases in the solid solution when the applied RF power increases, followed by a scale transformation from applied power to parameter using the Boltzmann equation. The Ba/Sr ratio was obtained from X-ray energy dispersive spectroscopy; the comparison with the X-ray diffraction derived composition shows a remarkable coincidence while the discrepancies offer a valuable diagnosis on the sputtering flux and phase composition. The proposed method allows a quick setup of the RF cosputtering system to control film composition providing a versatile tool to optimization of the process.

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