Studie van de waterige oplossinggel methode voor de bereiding van ferro-elektrisch lanthaan gesubstitueerd bismuttitanaat

Abstract

In this PhD research the synthesis of phase pure lanthanum substituted bismuth titanate (BLT) powders and the deposition of BLT thin films for application in non-volatile ferroelectric RAM has been investigated. The synthesis was carried out by means of several aqueous solution-gel routes, which have the advantage over alcoholic sol-gel of utilizing an inexpensive and safe solvent (H2O) and simple starting products. Furthermore, the aqueous precursors can be handled in ambient atmosphere, which simplifies the syntheses. An important objective of this research was to gain insight into the chemical mechanisms of all the different stages in this synthesis route, being 1) complexation of the metal ions with appropriate ligands to obtain stable, aqueous solutions and the prevention of precipitation due to hydrolysis and condensation; 2) formation of an amorphous, homogeneous gel depending on the composition of the solution (e.g. molar ratio ligand:Mn+) and its pH; 3) gel thermolysis, for the removal of the organic gel components; 4) crystallization of the pure desired phase. Homogeneity down to molecular level is enormously important during all these stages, in order to obtain the phase pure oxide at relatively low temperatures....