研究目的
Investigating the effect of rare earth element nature and role of Ln/Ba and Fe/Co ratio on the crystal structure and oxygen content for the Ba1-xLnxFe1-yCoyO3-δ (Ln = Pr, Sm, Gd; x = 0.3-0.4; y = 0-0.5) phases.
研究成果
The crystal chemistry of Ba1-xLnxFe1-yCoyO3-δ oxides is complex and dependent on cation nature and ratios, with Pr-containing systems forming disordered perovskites, Sm systems forming quintuple layered structures, and Gd systems forming triple or quintuple structures. Oxygen content variations are smaller in ordered phases, indicating implications for material properties in applications like solid oxide fuel cells.
研究不足
The study is limited to specific compositions and conditions (e.g., air atmosphere, 1100°C annealing), and the techniques used may not capture all structural details without complementary methods. Potential optimizations could include varying synthesis conditions or using additional characterization techniques.
1：Experimental Design and Method Selection:
The study involved preparing samples using the glycerin nitrate technique to synthesize Ba1-xLnxFe1-yCoyO3-δ oxides, with structural analysis via XRD and TEM, and oxygen content determination through thermogravimetry and iodometric titration.
2：Sample Selection and Data Sources:
Samples were selected based on compositions with x =
3：3-4 and y = 0-5, using high-purity starting materials including rare earth oxides, barium carbonate, metallic cobalt, and iron oxalate. List of Experimental Equipment and Materials:
Equipment included a Shimadzu XRD-7000 for XRD, JEOL JEM 2100 and FEI Technai G2 30 UT microscopes for TEM, and a STA 409PC instrument for TGA. Materials included Pr6O11, Sm2O3, Gd2O3 (≥
4：99%), BaCO3 (9%), Co, FeC2O4×2H2O (0%), nitric acid, and glycerin. Experimental Procedures and Operational Workflow:
Samples were prepared by dissolving materials in nitric acid, adding glycerin, heating to form a gel and powder, annealing at 1100°C for 120 hours with intermediate grindings, and slow cooling. XRD was performed in air with CuKα radiation, TEM images were collected from suspensions on carbon grids, and TGA was conducted from 25–1100°C in static and dynamic modes.
5：Data Analysis Methods:
Structural parameters were refined using the Rietveld profile method with Fullprof-2008 package, and oxygen content was analyzed based on iodometric titration and TGA results.
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