Ca₃Co₄O₉ is a p-type semiconducting material that is well-known for its thermoelectric (TE), magnetic, electronic, and electro-optic properties. In this study, sol-gel autoignition was used to prepare Ca₃Co₄O₉ at different calcination temperatures (773, 873, 973, and 1073 K) and time (4, 6, 8, 10, 12, and 14 h) using starch as a fuel. The phase and microstructure of the prepared Ca₃Co₄O₉ powder were investigated. Thermogravimetry.differential thermal analysis (TGA) confirms that the final weight loss occurred at 1073 K to form Ca₃Co₄O₉ stable powder. The variable-pressure scanning electron microscopy (VP-SEM) images show that the size of powder particles increases from 1.15 to 1.47 μm as calcination time increases from 4 to 12 h, and the size remains almost constant thereafter. A similar pattern is also observed on the increment of the crystallite size and percentage of crystallinity with X-ray diffraction (XRD) analysis. The highest crystallinity is found about 92.9% when the powder was calcinated at 1073 K for 12 and 14 h with 458 and 460 Å crystallite size, respectively. Energy dispersive X-ray spectroscopy (EDS) analysis demonstrates that the calcinated powder has a high intensity of Ca, Co, and O with uniform distribution. High-resolution transmission electron microscopy (HRTEM) images prove that there is no distinct lattice distortion defect on the crystal structure.

中文翻译：

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淀粉辅助溶胶-凝胶燃烧法合成的煅烧温度和时间对Ca 3 Co 4 O 9纯度的影响

Ca ₃ Co ₄ O ₉是一种p型半导体材料，以其热电（TE），磁，电子和电光特性而闻名。在这项研究中，使用溶胶-凝胶自燃技术在不同的煅烧温度（773、873、973和1073 K）和时间（4、6、8、10、12和14 h）下制备Ca ₃ Co ₄ O ₉。用淀粉作为燃料。研究了制备的Ca ₃ Co ₄ O ₉粉末的相结构和微观结构。热重分析。差示热分析（TGA）证实最终重量损失发生在1073 K处，形成Ca ₃ Co ₄ O ₉稳定的粉末。可变压力扫描电子显微镜（VP-SEM）图像显示，随着煅烧时间从4小时增加到12小时，粉末颗粒的尺寸从1.15微米增加到1.47微米，此后尺寸几乎保持恒定。通过X射线衍射（XRD）分析，在晶粒尺寸的增加和结晶度的百分比上也观察到类似的图案。当粉末分别以458和460Å的微晶尺寸在1073 K下煅烧12和14 h时，最高结晶度约为92.9％。能量色散X射线光谱（EDS）分析表明，煅烧后的粉末具有高强度的Ca，Co和O，且分布均匀。高分辨率透射电子显微镜（HRTEM）图像证明晶体结构上没有明显的晶格畸变缺陷。