Synthesis of La_1-xSr_xCoO₃ (x≤0.2) at Low Temperature from PVA-polymeric Gel Precursors

Single phase La_1-xSr_xCoO₃ (x≤0.2) was synthesized as a uniform sized 100 nm particulates with relatively high surface area of 20-30 m²/g, at low temperature (≥600°C), from a polymeric gel precursors prepared by using poly(vinyl alcohol) as homogenizer. No minor phase developed during the crystallization when polymer/metal mole ratio was higher than 3. As the polymer/metal mole ratio was raised in the gel, the amount of carbonaceous residues in the amorphous solid precursor prepared by heating the gel at 300°C increased. Most of the residues were eliminated by exothermic thermal decomposition around 400°C. The amount of residual carbon (less than 1%) left in the crystalline La_1-xSr_xCoO₃ decreased as more polymer was used, eliminating detrimental effect which might be posed by using large amount of organic homogenizer. The crystal structure of La_1-xSr_xCoO₃ synthesized at temperature lower than 800°C was observed to be shifted from rhombohedral to more symmetric cubic. The structure shifted back to rhombohedral as the cubic sample was annealed at 1000°C.