Infrared radiation performance and calculation of B-site doped lanthanum aluminate from first principles

Pure LaAlO₃ and LaAl_1-xNi_xO₃ samples (x?=?0.05, 0.1, 0.15, 0.2, 0.25, 0.3) were prepared using a sol-gel technique. The samples were analyzed and characterized using XRD, SEM, FT-IR and XPS. The results showed that the infrared emissivity of LaAl_1-xNi_xO₃ powder prepared at 1500?℃ for 2?h increases with Ni²⁺ doping content. For x?=?0.25, the mean emissivity in the 3–5?µm infrared spectral region was 0.835. This was a 142% increase compared with that of pure LaAlO₃ (0.345). The doped Ni ions mainly exist with valences of +?2 and +?3 in the LaAlO₃ lattice. After doping, the concentration of electron holes and oxygen vacancies increased, leading to an enhancement of free carrier absorption in the system. It indicated that the Ni²⁺ doping would introduce an impurity energy level in the forbidden band of LaAlO₃ by first principles calculation, forming primarily by the hybridization of the 3d orbital electrons of the Ni ions and the 2p orbital electrons of the oxygen atoms. When x?=?0.25, the band gap decreased from 3.50?eV to 0.77?eV. The impurity energy level allows for a reduction in the energy required for the electrons transferring from the valence band to the conduction band, causing increased numbers of electron transitions between the band gaps, thus enhancing free carrier absorption and increasing the infrared emissivity of the material. The LaAl_1-xNi_xO₃ oxide materials prepared in this work had excellent infrared radiation properties. As a lining material at high temperature reacting furnace, the energy loss could be reduced, the heat utilization efficiency would be greatly improved, and the utility model could be used in the field of high-temperature thermal energy saving.