Li_1.5Al_0.5Ti_1.5(PO₄)₃ (LATP) is considered to be one of the promising solid-state electrolytes owing to its excellent chemical and thermal stability, wide potential range (~5.0 V), and high ionic conductivity (~10^-4 S/cm). LATP powders are typically prepared via the sol-gel method by adding and mixing nitrate or alkoxide precursors with chelating agents. Here, the thermal properties, crystallinity, density, particle size, and distribution of LATP powders based on chelating agents (citric acid, acetylacetone, EDTA) are compared to find the optimal conditions for densely sintered LATP with high purity. In addition, the three types of LATP powders are utilized to prepare sintered solid electrolytes and observe the microstructure changes during the sintering process. The pyrolysis onset temperature and crystallization temperature of the powder samples are in the order AC-LATP > CA-LATP > ED-LATP, and the LATP powder utilizing citric acid exhibits the highest purity, as no secondary phase other than LiTi₂PO₄ phase is observed. LATP with citric acid and acetylacetone has a value close to the theoretical density (2.8 g/cm³) after sintering. In comparison, LATP with EDTA has a low sintered density (2.2 g/cm³) because of the generation of many pores after sintering.

Much research into fuel cells operating at a temperature below 800°C. is being performed. There are significant efforts to replace the yttria-stabilized zirconia electrolyte with a doped ceria electrolyte that has high ionic conductivity even at a lower temperature. Even if the doped ceria electrolyte has high ionic conductivity, it also shows high electronic conductivity in a reducing environment, therefore, when used as a solid electrolyte of a fuel cell, the powergeneration efficiency and mechanical properties of the fuel cell may be degraded. In this study, gadolinium-doped ceria nanopowder with Al₂O₃ and Mn₂O₃ as a reinforcing and electron trapping agents were synthesized by ultrasonic pyrolysis process. After firing, their microstructure and mechanical and electrical properties were investigated and compared with those of pure gadolinium-doped ceria specimen.

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