Lagetemperatuursdepositie en structuurvorming als nieuwe uitdagingen voor de waterige oplossing-gel route: een case studie met PbTiO3

Abstract

This research project is aimed at the synthesis of ferroelectric lead titanate (PbTiO3). At room temperature, this perovskite has a tetragonal crystal structure, allowing it to show ferroelectric behavior. Beyond the Curie temperature (490 °C) a structural ferroelectric–paraelectric phase transition is taking place towards a cubic crystal structure, causing the loss of all interesting properties. As opposed to other perovskite-type oxides, PbTiO3 has a simple phase diagram, which makes the ferroelectric phase relatively easy to obtain. Other systems often struggle with undesired side phases, rendering it hard to acquire the phase pure perovskite. Therefore, lead titanate is particularly suited to explore the synthesis possibilities of the aqueous solution-gel route, developed within the research group, for the preparation of int. al. multifunctional perovskite materials. Aqueous solution-gel systems, consisting of water-soluble metal complexes, are employed as starting point for the preparation of crystalline lead titanate. Through complexation of metal ions with electron donating groups, the hydrolysis and condensation reactions of the metal ions are impeded. Solvent evaporation induces the formation of amorphous gels through bridging reactions of metal ion complexes, which transform into the oxide after a thermal treatment. ...