Preparation of alkaline earth carbonates and oxides by the EDTA-gel process

The ethylene-diamine-tetra-acetic acid (EDTA)-gel process has been used to produce carbonates and oxides of the alkaline earth elements Ba, Sr and Ca and their solid solutions. These materials have a range of potential applications including electron emission and catalysis. Gels of composition Ba-EDTA, Sr-EDTA, [Ba0.5Sr0.5]-EDTA, [Ba0.5Sr0.45Ca0.05]-EDTA were prepared at pH 6 from aqueous solutions of the alkaline earth nitrates and EDTA and their thermal decomposition studied by TGA/DSC. The gels and the products derived from calcination of these gels at different temperatures have been characterised by FTIR, XRD and SEM, and shown to have high chemical homogeneity and fine particle size. Decomposition of the gels to the carbonate form occurred below 300 degrees C with subsequent formation of the oxide occuring on heat treatment at temperatures ranging from approximately 800 degrees C to > 1000 degrees C depending upon gel composition. The process route is suitable for the production of particulate materials or porous coatings. (C) 2000 Kluwer Academic Publishers.