Freeze-dried acetates of La, Sr and Mn—reactive precursors of (La, Sr)(n+1)MnnO(3n+1)—compounds

Abstract

The thermal decomposition of freeze-dried acetate precursors for La-Sr-manganates was investigated by means of DTA, TG, mass spectroscopy and X-ray powder diffractometry. The decomposition of single manganese- and strontium acetate widely corresponds to the decomposition of crystalline acetates, well known from the literature. During the decomposition of lanthanum acetate in an inert argon atmosphere two intermediate lanthanum-oxo-acetates besides lanthanum-oxo-arbonate are formed. The decomposition of complex acetates reflects some aspects of the single acetates, but also an interaction between the components which results in a lower decomposition temperature. The solid phase formation after decomposition of precursors takes place at a significantly lower temperature in comparison to the solid state reaction of mixed oxides/carbonates. In this way, single phase layer manganates with K2NiF4-structure can be formed already by annealing the precursors at 1000°C. For the same result the solid state reaction of of mixed oxides needs an annealing temperature of 1350°C.