Contribution to the study of the sol-gel method for the preparation of perovskites: Synthesis and characterization of lead(zirconium titanium) oxygen and (lanthanum strontium)cobalt oxygen (Dutch text).

摘要

The thesis discusses the preparation, thermal treatment, phase formation and electrical properties of ferroelectric Pb(Zr_xTi_1-x)O ₃ (PZT) and conducting (La_1-xSr_x)CoO₃ (LSCO). The applied synthesis method is the so-called “sol-gel method”.; A PZT precursor solution is developed using dehydrated lead acetate, zirconium propoxide and titanium isopropoxide in butoxyethanol. Thermal decomposition of the precursor can be divided into evaporation of solvent residues, further condensation processes and decomposition of organic residual groups. Combination of several thermal analysis techniques allows us to describe occurring reactions. During pyrolysis the product remains amorphous, afterwards crystallization of perovskite PZT starts via pyrochlore. Titanium rich PZT's crystallize at lower temperatures than zirconium rich ones. As derived from the preparation scheme of PZT, also PTO (PbTiO₃), PLZT ((Pb,La)(Zr,Ti)O₃), TiO₂ and ZrO₂ can be synthesized.; Several efforts were made to prepare a good organic sol-gel precursor for LSCO, however results are reprehensible due to strong reactivity differences between the metals in question. Water based acetate and nitrate sol-gel methods that incorporate bridging or chelating reagents yield far better homogeneity properties. The nitrate gel seems to have the best phase purity when calcinated above 900°C, as sintered nitrate and acetate based oxides have excellent homogeneity and phase purity.