Chemical interactions between 3 mol% yttria-zirconia and Sr-doped lanthanum manganite

The chemical interactions between porous (La 0.8Sr 0.2)MnO 3 (LSM) film and 3 mol% yttria tetragonal zirconia (TZ3Y) substrate have been investigated over the temperature range of 1300–1500 °C in air. Two distinct reaction layers of fluorite-type cubic zirconia solid solution c-(Zr,Mn,La,Y)O 2 and lanthanum zirconate pyrochlore (La,Sr) 2(Zr,Y) 2O 7 were observed at the interface of LSM/TZ3Y. It has been found that the diffusion/dissolution of Mn ions in TZ3Y leads to the formation of the fluorite-type cubic zirconia solid solution, while the interaction of lanthanum with TZ3Y results in the formation of the lanthanum zirconate pyrochlore phase. Phase studies in the (ZrY)O 2–La 2O 3–Mn 3O 4 system show that the fluorite-type cubic zirconia solid solution phase c-(Zr,Mn,La,Y)O 2, rather than the tetragonal 3 mol% Y 2O 3–ZrO 2 phase, is in equilibrium with LSM perovskite at high temperatures. A ternary phase diagram of the system at the (ZrY)O 2-rich end at 1400 °C in air was proposed based on the experimental results. It is suggested that the fundamental reason for the beneficial effect of A-site non-stoichiometry or Mn excess of LSM in the inhibiting of the lanthanum zirconate formation is due to the fact that Mn 3O 4 does not equilibrate with lanthanum zirconate at high temperatures.