The effect of CuFe2O4 ferrite phase evolution on 3–5 μm waveband emissivity

• Published in: Ceramics international 2020-04, Vol.46 (6), p.7694-7702
• Main Authors: Zhang, Jian, Bai, Hao, Han, Ye, Wang, Fei, He, Simei, Liu, Pengfei, Zhang, Xu, Yuan, Huanmei, Zhang, Zefei
• Format: Article
• Language: English
• Subjects: CuFe2O4 ferrite; First principle calculations; Infrared radiation; Optical properties; Phase transformation
• ISSN: 0272-8842; 1873-3956
• DOI: 10.1016/j.ceramint.2019.11.272

CuFe2O4 ferrite is considered to be a promising material to improve the radiation heat transfer of industrial furnaces due to its high infrared emissivity in middle and short wavebands. CuFe2O4 ferrites were prepared by sintering at different temperatures (800, 900, 1000, 1100 and 1200 °C). The thermal behaviour and phase composition were measured by differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The results validate that the I41/amd structure of CuFe2O4 ferrite transforms to the Fd-3m structure at temperatures above 1000 °C. The cation valence states of CuFe2O4 ferrite with I41/amd and Fd-3m structures were determined by X-ray photoelectron spectroscopy. Through the analysis of the results, it is found that there are differences for the ratio of Cu+/Cu2+ and Fe2+/Fe3+ between the two structures of I41/amd and Fd-3m, which can be attributed to the existence of oxygen vacancy. The different vibrations of metal oxides were measured by Raman spectroscopy, which confirmed the formation of oxygen vacancy. With first principle calculations, the electron transition properties and optical absorption coefficients of the I41/amd and Fd-3m structures were calculated and compared. The calculation results show that the band gap of Fd-3m structure is 0.798eV, which is higher than that of I41/amd structure (0.573eV). This indicates that compared with I41/amd structure, Fd-3m structure has no advantage in improving the emissivity of 3–5 μm waveband. However, VO can introduce donor level into the band gap, which plays a key role in reducing the band gap and increasing the emissivity of 3–5 μm waveband. In the first principle calculations, VO was introduced to calculate the absorption coefficient of Fd-3m structure. It is found that the absorption coefficient of CuFe2O4 ferrite with Fd-3m structure in 3–5 μm waveband is higher than that of I41/amd structure, which indicates that VO can improve the optical absorption of 3–5 μm waveband, so as to improve the emissivity of corresponding waveband. By measuring the emissivity of 3–5 μm waveband, it is verified that the emissivity of Fd-3m structure (0.88) is higher than that of I41/amd structure (0.71). •The phase evolution of CuFe2O4 ferrite was analysed by sintering.•The electronic properties of CuFe2O4 ferrite were calculated by first principles.•Vo induces donor levels and narrows the band gap increasing electron transitions.•The 3–5 μm emissivity of 0.88 for Fd-3m is higher than that of 0.71 for I41/am