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Abstract: In this work, Ba x Sr1−x TiO3 sol–gel thin films (x =0.7, 0.5 and 0.3) deposited on Pt/Si substrate and post-annealed at different temperatures have been investigated. A systematic study of the structure, microstructure and dielectric properties has been achieved for each composition. To our knowledge, for the first time, a systematic effect of post-deposition annealing temperature and composition is reported. For each Ba/Sr ratio, higher annealing temperature leads to crystallinity improvement and to grain growth. A shift of the ferroelectric to paraelectric transition toward the bulk Curie temperature with the increase of the annealing temperature is shown. These results are correlated with the increase of the permittivity, tunability and dielectric losses measured on MIM capacitors at low frequency. Moreover, the high frequency results, between 800MHz and 30GHz, are in very good agreement with low frequency measurements, and show a huge tunability up to 80% under 600kV/cm. [Copyright &y& Elsevier]

Abstract: Supercritical fluids have been used to prepare alumina powders. This versatile technique allows the tuning of the crystallinity of the obtained powders by a simple modification of the fluid''s nature. Amorphous or boehmite alumina could be successfully synthesised using either CO2/Ethanol or H2O/Ethanol, respectively. The two powders present very different sintering paths, which have been correlated to the grain morphology and crystalline state of the powders. We have established that the alumina elaborated in CO2/ethanol exhibited a significant decrease of the γ-Al2O3 →α-Al2O3 transition temperature resulting in a lower densification temperature. [Copyright &y& Elsevier]