SYNTHESIS OF LA1-XSRXCOO3 (X-LESS-THAN-OR-EQUAL-TO-0.2) AT LOW-TEMPERATURE FROM PVA-POLYMERIC GEL PRECURSORS

Single phase La1-xSrxCoO3 (x less than or equal to 0.2) was synthesize d as a uniform sized 100 nm particulates with relatively high surface area of 20-30 m(2)/g, at low temperature (greater than or equal to 600 degrees C), from a polymeric gel precursors prepared by using poly(vi nyl alcohol) as homogenizer. No minor phase developed during the cryst allization when polymer/metal mole ratio was higher than 3. As the pol ymer/metal mole ratio was raised in the gel, the amount of carbonaceou s residues in the amorphous solid precursor prepared by heating the ge l at 300 degrees C increased. Most of the residues were eliminated by exothermic thermal decomposition around 400 degrees C. The amount of r esidual carbon (less than 1%) left in the crystalline La1-xSrxCoO3 dec reased as more polymer was used, eliminating detrimental effect which might be posed by using large amount of organic homogenizer. The cryst al structure of La1-xSrxCoO3 synthesized at temperature lower than 800 degrees C was observed to be shifted from rhombohedral to more symmet ric cubic. The structure shifted back to rhombohedral as the cubic sam ple was annealed at 1000 degrees C.