Preparation of LSGM electrolyte via fast combustion method and analysis of electrical properties for ReSOC.

Abstract

In this work, we prepared La_1 − xSr_xGa_1−yMg_yO₃ (LSGM) by the fast combustion method and assessed the electrical properties with respect to the composition and sintering temperature (1200, 1300, and 1400 °C by 6 h) as an electrolyte material for the reversible solid oxide cells (ReSOCs). For the preparation of samples, two different fuels, such as tartaric acid (TA) and citric acid (CA), with corresponding nitrate salts as precursors, were adopted for the fast combustion method (at 500 °C for 10 min). From the X-ray diffractograms, two main phases corresponding to LSGM orthorhombic (space group Imma) and LSGM-cubic (space group Pm-3 m) were identified. From the literature, both structures are reported as high oxygen ion conductive species, but normally they are not reported to appear together. Additionally, in some cases, an isolating (secondary) phase of LaSrGaO₄ in a low concentration < 1.98% was observed. The scanning electron microscopy (SEM) studies on samples sintered at 1200 and 1300 °C revealed the smaller grain size and irregular morphology. The SEM micrographs depicted a well-defined superficial morphology with less porosity for the samples sintered at 1400 °C. For comparative analysis, the conductivity (S.cm^− 1) was measured at varying temperatures (300–800 °C) for the samples sintered at 1300 and 1400 °C. Because of the large number of insulating phases produced by the incomplete sintering process, the samples sintered at 1300 °C had lower conductivities. A higher conductivity of 0.125 S.cm^− 1 was observed for La_0.80Sr_0.20Ga_0.80Mg_0.20O₃ (LSGM), which was obtained using the citric acid (sintered at 1400 °C), which is in the range of earlier reported similar studies. The observed variation in the conductivity with respect to different phases of LSGM, the influence of the secondary phase, and the wt% of the constituents of LSGM are discussed.