Auto-ignition synthesis of nanocrystalline BaTi4O9 powder

Monophasic BaTi4O9 powder has been prepared by an auto-ignition route. The auto-ignition of the gel, prepared by thermal dehydration of a pH adjusted citrate-nitrate solution, directly resulted in voluminous BaTi4O9 powder with traces of carbonaceous material. Calcination of the voluminous powder at 600 degreesC produced pure nanocrystalline BaTi4O9 powder. Process parameters such as the amount of citric acid used for gelation and pH of the starting solution were found to have a signifant influence on the gel stability, temperature required for the phase formation and the powder characteristics. TEM micrographs revealed the nanocrystalline nature (crystallite size < 50 nm) of the powder. BaTi4O9 powder when cold pressed and sintered at 1200 °C for 6 hours in air reached ≈ 96% of its theoretical density.