Synthesis of complex metal oxides using hydroxide, cyanide, and nitrate solid solution precursors

Precursor solid solutions provide convenient routes for preparing complex metal oxides. Hydroxide solid solutions of the general formula Ln 1−x M x (OH)3 (where Ln = La or Nd and M = Al, Cr, Fe, Co, or Ni) and La1−x−y M′ x M″ y (OH)3 (where M′ = Ni and M″ = Co or Cu) crystallize in the rare earth trihydroxide structure and can be decomposed at relatively low temperatures to yield complex metal oxides. Several oxides of the type LaNiO3, NdNiO3, LaNi1−x Co x O3, and LaNi1−x Cu x O3 have been prepared by the hydroxide precursor route. Thermal decomposition of cyanide precursors of the type Ln[M 1−x M′ x (CN)6] · 5H2O and Ln 1−x Ln′ x [M(CN)6] · 5H2O yields the quaternary oxides which are not readily made by ceramic methods. Nitrate solid solution precursors of the type Ba1−x Pb x (NO3)2, Sr1−x Pb x (NO3)2, and BaSrPb(NO3)6 have been used for preparing several interesting oxides such as BaPbO3, Ba2PbO4, and BaSrPbO4.