Phase Equilibrium in the System Ln–Mn–O: II. Ln=Nd at 1100°C

Phase equilibrium is established in a Nd–Mn–O system at 1100°C by changing the oxygen partial pressure from 0 to 12.00 in log(Po2/atm); a phase diagram at 1100°C is presented for a Nd2O3–MnO–MnO2 system. Under the experimental conditions, Nd2O3, MnO, Mn3O4, and NdMnO3 phases are present at 1100°C, but Nd2MnO4, Mn2O3, and MnO2 are not stable in the system. Wide ranges of nonstoichiometry were found in the NdMnO3 phase, which coexisted with Nd2O3. X ranges from 0.006 at log Po2=-10.85 to 0.104 at log Po2=0 in the form of NdMnO3+X. The nonstoichiometry is represented by the equation No/NNdMnO3=4.34×10-5(log Po2)3+1.99×10-3(log Po2)2+2.65×10-2(log Po2)+0.104; the activities of the components in the solid solution are also calculated with this equation. NdMnO3 has a composition range to the Nd2O3-rich or Nd2O3-poor side of LaMnO3. Lattice constants of NdMnO3 made in different oxygen partial pressures were determined.