Abstract

Monophasic Ba₂Ti₉O₂₀ has been prepared using the powder derived through an auto-ignition route. The process involves the formation of a viscous gel by thermal dehydration of the pH adjusted citrate–nitrate solution. The process parameters, for example, the amount of citric acid used for gelation and pH of the starting solution were optimized experimentally to get a stable gel with a desired decomposition behavior and favorable powder characteristics. The auto-ignition (at an external temperature of ≈225 °C) of the gel resulted in a voluminous, nanocrystalline (<50 nm) powder containing intimate blending of BaTi₄O₉ and TiO₂ with traces of carbonaceous material. The monophasic Ba₂Ti₉O₂₀ could be obtained at a calcination temperature of 1200 °C. The powder obtained after auto-ignition, when calcined at 600 °C and sintered at 1250 °C for 6 hours, produced ≈96% dense, phase pure Ba₂Ti₉O₂₀.