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

Abstract

Precursor solid solutions provide convenient routes for preparing complex metal oxides. Hydroxide solid solutions of the general formula Ln_1-xM_x(OH)₃ (where Ln = La or Nd and M = Al, Cr, Fe, Co, or Ni) and La_1-x-yM'_xM’_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, LaNi_1-xCo_xO₃, and LaNi_1-xCu_xO₃ have been prepared by the hydroxide precursor route. Thermal decomposition of cyanide precursors of the type Ln[M_1-xM'_x(CN)₆] · 5H₂O and Ln_1-xLn'_x[M(CN)₆] · 5H₂O yields the quaternary oxides which are not readily made by ceramic methods. Nitrate solid solution precursors of the type Ba_1-xPb_x(NO₃)₂, Sr_1-xPb_x(NO₃)₂, and BaSrPb(NO₃)₆ have been used for preparing several interesting oxides such as BaPbO₃, Ba₂PbO₄, and BaSrPbO₄.