Ammonium barium citrato peroxotitanate(IV) Ba2(NH4)2[Ti4(O2)4(Hcit)2(cit)2] · 10H2O: a molecular precursor of stoichiometric BaTi2O5

Diammonium dibarium hydrogen citrato peroxotitanate(IV), Ba2(NH4)2[Ti4(O2)4(Hcit)2(cit)2] · 10H2O, is obtained directly from H2O2 oxidation of tricitrato titanate, or from the reaction of peroxotitanate with citric acid (H4cit=citric acid), which is decomposed stoichiometrically into BaTi2O5 at the temperature of 800 °C in air.