Interaction of perovskite type lanthanum-calcium-chromites-titanates La_(1-x)Ca_xCr_(1-y)Ti_yO_(3-δ) WITH solid electrolyte materials

摘要

Lanthanum-calcium-chromites-titanates have been proposed as alternative anode material ~(1,2), and diffusion barrier layer material for metal supported cells~3, due to their electrical conductivity and acceptable coefficients of thermal expansion. However interactions of perovskites with electrolyte materials such as doped zirconia are known to cause zirconate formation depending on temperatures and oxygen partial pressure ~4. In this study we demonstrate how the presence of metallic nickel at the phase boundary affects the zirconate formation at the solid state perowskite-fiuorite interface. Different compositions of La_(1-x)Ca_xCr_(1-y)Ti_yO_(3-δ) (x= 1, 0.95, 0.7, 0.6, 0.5, 0.4; y = 1, 0.9, 0.8) were synthesized and reactivity with yttria doped zirconia (8YSZ) and nickel-8YSZ-cermets have been investigated by means of X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy after 80 hours at 1300°C in reducing atmosphere (H_2). The results indicate that under certain conditions there is no zirconate formation in the absence of nickel, whereas if nickel is present at the interface, calcium- and or lanthanum zirconate formation take place, depending on the La/Ca-ratio of the A-site doping. Thermodynamic calculation and EDX spectra consistently indicate nickel-titanium alloy formation as a reason for the destabilization of the perovskite lattice within a range of 10~(-19.4)< a(O_2) < 10~(-16.5)at 1300°C .