Investigation of the Amount of Polyvinylpyrrolidone as Gelling Agent to Lanthanum Cobaltite Micropowders Synthesized by Sol-Gel Method

The paper focuses on lanthanum cobaltite micropowders LaCoO3-delta (LCO) synthesized by the sol-gel method using polyvinylpyrrolidone (PVP) as a gelling agent. The PVP content was varied from 0.5 to 5.0 wt % when ionic solutions of the soluble raw components were prepared. The gels were dried in a microwave oven at a microwave power of 90 W for 2 h to evaporate water. Xerogels were thermally treated in a muffle furnace at temperatures 800 and 900 degrees C; the maximum holding time was 10 and 30 h. After heat treatment of xerogels at 800 degrees C for 10 h, the LCO micropowders were slightly aggregated, the particle size was in the range from 0.24 to 0.38 mu m, and the specific surface area was in the range from 2.60 to 4.10 m(2)/g. After heat treatment at 900 degrees C for 10 h, the range of the specific surface area of LCO micropowders decreased from 1.00 to 3.20 m(2)/g, but particle size range slightly increased from 0.31 to 1.0 mu m. The heat treatment of xerogels at a temperature 900 degrees C for 30 h resulted in the particles size range growing from 0.50 to 1.25 mu m, and the specific surface area was 2.00 m(2)/g for all LCO micropowders. There was no effect of PVP content in the ionic solution on the phase composition for all heat-treated LCO micropowders.