Preparation of La0.75Sr0.25MnO3 nano-phase powders and films from alkoxide precursors

The first purely alkoxide-based sol-gel route to nano-phase powders and thin films of perovskite La0.75Sr0.25MnO3 is described. The phase and microstructure evolution on heat treatment of free gel films to form the target nano-phase oxide were investigated by TGA, IR spectroscopy, powder XRD, SEM and TEM-EDS. The xerogel consisted of a hydrated oxo-carbonate, without remaining alkoxo groups or solvent. Heating at 5degreesC.min(-1) decomposed the carbonate groups and yielded the pure perovskite La0.75Sr0.25MnO3 at 760degreesC. The cell dimensions were virtually unchanged from the first observation of perovskite at 680degreesC, to 1000degreesC, 4 h. The monoclinic cell of La0.75Sr0.25MnO3 obtained at 1000degreesC, 4 h, had the dimensions a = 5.475(1), b = 5.504(2), c = 7.771(1) Angstrom beta = 90.50(2), fitting the literature data quite well. Crack-free, homogenous, 150 nm thick La0.75Sr0.25MnO3 films were prepared by spin-coating Si/SiO2/TiO2/Pt and polycrystalline-Al2O3 substrates with a 0.6 M alkoxide solution, followed by heating at 5degreesC.min(-1) to 800degreesC, 30 min.