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

✍ Scribed by Kenzo Kitayama

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 151 KB
• Volume: 153
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.2000.8779

✦ Synopsis

are not stable. Wide ranges of nonstoichiometry were found is the LaMnO 3 phase.

x ranges from ؊0.050 at log P O2 ‫؍‬ ؊13.05 to 0.18 at log P O2 ‫؍‬ 0 in the form of LaMnO 3؉x . The nonstoichiometry is represented with the equation, N O /N LaMnO3 ‫؍‬ 1.94؋10 ؊4 (log P O2 ) 3 ؉ 5.24؋10 ؊3 (log P O2 ) 2 ؉5.24؋10 ؊2 (log P O2 )؉0.179, and activities of the components in the solid solutions are calculated using this equation. LaMnO 3 seems to have a range of compositions from La 2 O 3 -rich to poor. Also MnO has a small nonstoichiometry at the oxygen-rich side. Lattice constants of LaMnO 3 were determined at di4erent oxygen partial pressures. The crystal form of LaMnO 3 seems to change from orthorhombic to hexagonal as the oxygen partial pressure becomes higher. The standard Gibbs energy changes of the reactions in the phase diagram presented were calculated.