Ternary Compounds in the System La‐Co‐O

The compounds LaCoO 3 , La 4 Co 3 O l0 , and La 2 CoO 4 were synthesized and characterized by powder X‐ray diffraction. Lanthanum cobaltate, LaCoO 3 , has the rhombohedra1 modification of the perovskite structure, whereas La 4 CO 3 O 10 and La 2 CoO 4 have perovskite‐related structures based on face‐centered orthorhombic lattices. The lattice parameters of these ternary phases are dependent on the conditions of preparation. Six invariant reactions in the system La‐Co‐O are summarized in a portion of the 1130°C isothermal section.