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

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 degreesC. For the same result the solid state reaction of of mixed oxides needs an annealing temperature of 1350 degreesC. (C) 2002 Elsevier Science B.V All rights reserved.