Influence of A-site nonstoichiometry on microstructure and electrical properties of (La0.9Sr0.1)xGa0.8Mg0.2O3-δ(x = 0.97, 1.00, 1.03) electrolyte materials

The intermediate-temperature solid electrolyte with distorted perovskite lattice (La0.9Sr0.1)xGa0.8Mg0.2O3-δ (x = 0.97, 1.00, 1.03) was synthesized by a modified sol-gel method. The characterization was carried out using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), and electrical properties of the sintered samples were studied by A.C. impedance technology. The XRD patterns indicate that these materials are single phases of an orthorhombic perovskite-structure with the presences of small amounts of secondary phase. Impedance spectroscopy was measured in the temperature range between 400 °C and 800 °C. It shows the highest conductivity when x = 1.03 (σt = 10.45 × 10−4, σgb = 25.12 × 10−4 S cm−1 at 450 °C). The distorted perovskite lattice suppressed the order of oxygen sublattice which introduces A-site cation excess. And thus improved physical and electrical property was achieved in the sample.

Images with no abnormal grain growth and the grains are in close contact to each other. The pellets are relatively dense, the relative density could reach above 93％. The excess A-site elements promote the grain growth, while the average grain size of A-site deficiency decreased. The above phenomena suggest that the excess A-site composition can improve sintering, it may be due to the large distortion of the surrounding lattice promote grain growth and densification at the same time.Figure optionsDownload as PowerPoint slide