Reactions of La1-xNdxSrCoO4 Ruddlesden-Popper phases under reducing atmospheres

Abstract

The reactions and behavior of La1-xNdxSrCoO4 Ruddlesden-Popper phases were investigated under vacuum and hydrogen atmospheres with varying Nd content (x = 0, 0.25, 0.5, 0.75, 1) and temperatures ranging from 250 to 720◦C. Under vacuum (total pressure between 4 and 5 ×10 3 mbar, pO2 = 10 3 mbar), linear thermal expansion is observed up to around 450◦C, followed by continuous formation of La1-xNdxSrCoO4-δ phases up to about700◦C, where decomposition into individual oxides (La2O3, Nd2O3, SrO) and Co occurs. La1-xNdxSrCoO4-δ formation starts at lower temperatures with increasing Nd content, and contrary to LaSrCoO4, with addition of Nd, La1-xNdxSrCoO4-δ formation completes before phase decomposition occurs. Under hydrogen atmosphere (5 %H2-95 %Ar), the reduction reaction La1-xNdxSrCoO4 + δ H2(g) = La1-xNdxSrCoO4-δ + δ H2O(g) initiates at about300◦C and completes around 400 ◦C, yielding the La1-xNdxSrCoO3.5 phase, with higher reactivity observed for x =0.5 among different Nd contents.