Synthesis of SrBi2Ta2O9 (SBT) by means of a soluble Ta(V) precursor

Aqueous sol-gel processing of pentavalent metals like Ta and Nb is very complicated since the only water soluble compound is the oxalate, which is not very suited for gel formation. Nevertheless, starting from Ta oxalate, it is possible to prepare a water soluble Ta(V) precursor that remains stable in the pH range needed for gel formation. During synthesis the oxalate is oxidized with H2O2 and subsequently complexed with citric acid and as a result the peroxo–citrato tantalum(V) complex is formed. This Ta(V) precursor is afterwards used for the synthesis of the ferroelectric SrBi2Ta2O9 (SBT). The formation of the SBT crystalline phases was investigated by means of high temperature X-ray diffraction (HT–XRD).