Structural, thermal and electrical conductivity characteristics of Ln0.5Sr0.5Ti0.5Mn0.5O3±d (Ln: La, Nd and Sm) complex perovskites as anode materials for solid oxide fuel cell

• Ln0.5Sr0.5Ti0.5Mn0.5O3±d oxide systems do not react with 8YSZ and CGO91.
• LSTM, NSTM and SSTM show orthorhombic symmetry with the space group Pbnm.
• LSTM shows relatively lower onset temperature in Ln0.5Sr0.5Ti0.5Mn0.5O3±d.
• Electrical conductivity values of NSTM are higher than those of LSTM and SSTM.

The Ti and Mn replaced complex perovskites, Ln0.5Sr0.5Ti0.5Mn0.5O3±d (Ln: La, Nd and Sm), were reported as potential anode materials for high temperature-operating solid oxide fuel cells (HT-SOFCs). For the present research study, synthesis, crystallographic, thermal and electrical conductivity properties of Ln0.5Sr0.5Ti0.5Mn0.5O3±d complex perovskites were investigated using X-ray diffraction (XRD), Rietveld method, thermogravimetric analysis (TGA) and electrical conductivity to apply these oxide materials for the HT-SOFC anode materials.XRD results showed that Ln0.5Sr0.5Ti0.5Mn0.5O3±d oxide systems synthesized as single phases did not react with 8 mol% yttria stabilized zirconia (8YSZ) and 10 mol% Gd-doped cerium oxide (CGO91) up to 1500 °C and did not decompose under dry 3.9% hydrogen at 850 °C. The crystal structures of La0.5Sr0.5Ti0.5Mn0.5O3±d (LSTM), Nd0.5Sr0.5Ti0.5Mn0.5O3±d (NSTM) and Sm0.5Sr0.5Ti0.5Mn0.5O3±d (SSTM) showed orthorhombic symmetry with the space group Pbnm and SSTM showed a more distorted structure. Thermogravimetric analysis (TGA) proved weight gains in these three sample occurred under oxidizing conditions and weight loss under reducing conditions. Electrical conductivity values of NSTM were higher than those of LSTM and SSTM under oxidizing and reducing conditions.

The B-site cations (Ti/Mn) are surrounded by regular octahedra of oxygen in Nd0.5Sr0.5Ti0.5Mn0.5O3±d(NSTM). These octahedra are linked together in a corner sharing three dimensional framework, while Nd/Sr ion occupies 12-coordinated A-site between these octahedra. The Ti/Mn–O6 octahedra are elongated along the c-axis. The crystal structure distortion was due to the smaller ionic radius of the A-site cations, which force the (Ti/Mn)–O6 octahedra to tilt in order to optimize the A–O bond distances. The same structural symmetry was found when the samples were reduced in 3.9% H2 in Ar at 900 °C for 12 h.Figure optionsDownload as PowerPoint slide