STUDIES ON OXYGEN DISSOCIATION PRESSURE OF LNMNO(3) (LN EQUALS RARE-EARTH) WITH THE EMF TECHNIQUE

The oxygen dissociation pressure of LnMnO(3) (Ln = La, Pr, Nd, Sm, Eu; Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y or Sc) was measured at high tempera ture (1170-1400 K) by means of e.m.f. using stabilized ZrO2 as a solid electrolyte. Assuming that the decomposition reaction proceeds in a s toichiometric form, a standard Gibbs free energy change of decompositi on was determined from the oxygen dissociation pressure. The variation of the free energy change with change in identity of Ln was investiga ted. It was found that the energy change depends strongly upon both th e crystal structure and the ionic radius of Ln(3+). The standard Gibbs free energy change of formation for LnMnO(3) compounds was obtained f rom the standard Gibbs free energy change for the decomposition reacti ons and those for the formation of the decomposition materials.