Infrared properties of Mg-doped LaFeO3 prepared by sol–gel method

A perovskite LaFe 1− x Mg x O 3 ( x = 0, 1/3) compound was prepared by the sol–gel method and characterized by TG–DTA, XRD, SEM, and XPS. The infrared (IR) emissivity of the nanoscale LaFe 2/3 Mg 1/3 O 3 powder synthesized after heat preservation for 2 h at 1300 °C was as high as 0.93 in the range 0.2–2 μm, an increase of 121 % than that of undoped LaFeO 3 . The increase in the IR emissivity of LaFe 2/3 Mg 1/3 O 3 can be mainly attributed to the substitution of Mg 2+ with Fe 3+ in the LaFeO 3 lattice. The substitution of Mg 2+ with Fe 3+ introduced the energy level of Fe 4+ impurity and generated oxygen vacancies, thus increasing the impurity and oxygen vacancy absorption. The lattice distortion caused by doping strengthened the lattice vibration absorption. The polaron hopping of electrons between Fe 3+ and Fe 4+ also significantly strengthened the absorption properties within the corresponding spectrum area of Mg 2+ -doped LaFeO 3 . Graphical Abstract The absorptivity of LaFeO 3 was stable at ~0.94 in the range 200–500 nm and decreased drastically after 500 nm, and the absorption edge was ~600 nm. The absorption of Mg-doped LaFeO 3 sample was 0.93 in the range 200–2000 nm. Mg doping significantly improved the absorptivity of LaFeO 3 (0.75); moreover, the absorption edge red-shifted to the spectral region at ~2000 nm. This was caused by the introduction of Mg 2+ that increased the oxygen vacancy concentration in LaFeO 3 valence band and enhanced the intraband absorption, thus strengthening the absorptivity to some extent.