The far-infrared emissivity and near-infrared reflectance of Mg1-xMnxFe2O4 synthesized by xerogel-microwave method

作者：Xiong, Canguang^*; Liu, Ping; Chen, Minggan; Cao, Xiuhua; Wang, Hui^*

来源：Journal of Alloys and Compounds, 2020, 836: 155516.

DOI：10.1016/j.jallcom.2020.155516

• Sol-gel
• Microwave
• Near-infrared reflectance
• Far-infrared emissivity

Red and brown inorganic pigments Mg1-xMnxFe2O4 (x = 0.0, 0.2, 0.3, 0.4, 0.5) with high far-infrared emissivity and high near-infrared reflectivity were synthesized by the xerogel-microwave method. The pure spinel structure of compounds was confirmed by various methods (X-ray diffraction (XRD), Fourier transform infrared spectrum (FTIR), and Raman spectroscopy). From the XRD analysis, we can find that a shift in the decreased XRD angle is observed with the addition of the Mn2+ ions because of the radius differences between host ions (Mg2+) and dopant ions (Mn2+) as well as the John-Teller distortion. Furthermore, the results of XRD and Raman spectroscopy demonstrated that Mn dopants can inhibit the grain growth. Meanwhile, the reflective properties were measured by UV-vis-NIR spectrophotometer and the NIR solar reflectance values in the 1400-2500 nm range are over 66% with a maximum 82.9% (x = 0.2). In the experiment where Mn2+ replaced Mg2+ in MgFe2O4, the band gap decreased from 2.14 eV to 1.86 eV, which results in the decrease of the NIR solar reflectance in 800-1400 nm range. At last, the infrared emissivity of the samples was measured at room temperature, and the average emissivity is over 0.8 with maximum 0.85 (x = 0.5), which is due to the lattice distortion and the intensification of asymmetrical vibration of the Mn-0, Mg-O and Fe-O bonds.