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Yttria-doped zirconia, lead zirconate titanate (PZT) and barium titanate were successfully obtained using hydrothermal procedures. Based on these results mathematical models describing the correlation between the nanopowders’ characteristics and the main synthesis parameters are proposed. Powders from the systems (Y2O3)0.1 (ZrO2)0.9 and (Y2O3)0.04 (ZrO2)0.96 obtained from soluble Zr(IV) peroxide precursors show that cubic/tetragonal phases have been formed by controlled crystallization from the solution. With increasing temperature and hydrothermal treatment temperature the mean crystallite sizes increase from a minimum of 5 nm to a maximum of 22 nm. The activation energy shows a diffusion-controlled process. Barium titanate powders with controlled stoichiometry could also be hydrothermally synthesized in the temperature range 110– 175°C. Synthesis of PZT powders with controlled stoichiometry and mean crystallite sizes from 4 to 43 nm is finally presented. Dense yttria-partial stabilized zirconia with high ionic conductivity and PZT with a good stability of electric–physical parameters for use in the design of materials with improved sensorial characteristics was obtained after sintering the nanopowders.

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In this paper, a hydrothermal method of high-pressure and low-temperature synthesis conditions is presented as a simple single-step technique to obtain crystalline nanoparticles of iron oxides. The aim of this work has been to demonstrate the influence of the main synthesis parameters on the formation of nanosized Fe2O3 particles using statistical methods and to establish the most significant effects. Based on mathematical pre-modeling calculations, the best reaction conditions for the hydrothermal process have been chosen, and controlled crystalline nanostructures of iron oxides could be prepared