Iron chromite powders were synthesized via solution combustion route using iron(III) nitrate nonahydrate and chromium(III) nitrate nonahydrate as starting materials, as well as glycine–urea, glycine–citric acid, and glycine–ethylene glycol mixtures as fuels. The effect of postheating at different temperatures on the structure, molecular, microstructure, and chromatic properties of powders and tiles colored by in-glaze powders was studied. The X-ray diffraction patterns showed that as-synthesized powders were obtained in crystalline FeCr₂O₄ phases moreover, postheating of the powders led to d-space shift and oxidation and formation of (Fe,Cr)₂O₃ solid solution phase regardless of fuel type. Phase transformation of FeCr₂O₄ to (Fe,Cr)₂O₃ solid solution was observed at 500/750°C depending on the dominant phase of as-synthesized particles. Fourier transform infrared analysis illustrated that the band positions of octahedral M–O and tetrahedral M–O bonds were shifted due to Fe cations movement from their position and lattice shrinkage by increasing of post-heating temperature. Moreover, scanning electron micrographs showed that Fe_0.7Cr_1.3O₃ semispherical fine particles were formed from porous spongy FeCr₂O₄ particles due to oxidation and phase transformation during the postheating. Furthermore, chromatic properties of the samples were represented. The color properties of the pigments showed that the formation of brown pigments is provided with the phase transformation from FeCr₂O₄ to (Fe,Cr)₂O₃ at a temperature of up to 750°C. Moreover, increasing the color purity to this temperature is related to the removal of residual carbonaceous matters. The chromatic properties of the glazed tiles colored using the pigments showed that postheating between 250 and 500°C led to more brown appearance.

中文翻译：

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FeCr2O4 到 (Fe,Cr)2O3 固溶体颜料粉末的相变：后加热温度的影响

以九水硝酸铁 (III) 和九水硝酸铬 (III) 为原料，以甘氨酸-尿素、甘氨酸-柠檬酸和甘氨酸-乙二醇混合物为燃料，通过溶液燃烧法合成亚铬铁粉。研究了不同温度后加热对釉内粉着色粉和瓷砖的结构、分子、微观结构和色彩特性的影响。X 射线衍射图表明合成后的粉末以结晶 FeCr ₂ O ₄相获得，而且粉末的后加热导致d空间位移和氧化并形成 (Fe,Cr) ₂ O ₃与燃料类型无关的固溶体相。在 500/750°C 下观察到FeCr ₂ O ₄到 (Fe,Cr) ₂ O ₃固溶体的相变，这取决于所合成颗粒的主要相。傅立叶变换红外分析表明，八面体 M-O 和四面体 M-O 键的能带位置发生了移动，这是由于 Fe 阳离子从它们的位置移动以及随着后加热温度的升高晶格收缩。此外，扫描电子显微照片显示，Fe _0.7 Cr _1.3 O ₃半球形细颗粒由多孔海绵状FeCr ₂ O _4形成由于后加热过程中的氧化和相变而产生的颗粒。此外，还表示了样品的色彩特性。颜料的颜色特性表明，棕色颜料的形成伴随着在高达 750°C 的温度下从 FeCr ₂ O ₄到 (Fe,Cr) ₂ O _{3的相变。}此外，将色纯度提高到该温度与去除残留的含碳物质有关。使用颜料着色的釉面砖的色彩特性表明，在 250 至 500°C 之间进行后加热会导致更棕色的外观。