采用高温固相烧结法在1 300 ℃反应2 h成功制备出钙钛矿型LaFe0.75Cr0.25O3和La0.75Mg0.25Fe0.75-Cr0.25O3粉体材料。通过XRD、FT-IR、SEM、XPS和Upward IntegratIRTM等对材料的物相结构和近中红外波段的发射性能进行分析表征, 并应用第一性原理计算分析了其电子结构, 研究影响发射率的理论机制。研究表明,粉体在1～5 μm波段的发射率都出现上升, 但Cr单掺试样的吸收率增幅不大, 而Mg-Cr共掺粉体增幅较大, 在近红外波区的吸收率在0.9以上。究其原因在于, Cr单掺后晶体发生畸变, 但不增加自由载流子的浓度, Mg-Cr共掺后畸变加剧且生成较多氧空位和小极化子, 强化了自由载流子的吸收。Cr 3d轨道与O 2p所形成的杂化能级和在近费米能级导带区的Cr 3d轨道造成了粉体禁带宽度变窄, Mg虽然未直接作用于带隙值, 但间接改变了B位元素的形态, 产生了更多的小极化子, 因此与LaFeO3禁带宽度值(3.817 eV)相比, Mg-Cr共掺(0.109 eV)减小幅度最大, Cr单掺(2.406 eV)次之。

Perovskite type LaFe0.75Cr0.25O3 and La0.75Mg0.25Fe0.75Cr0.25O3 powders were prepared by high temperature solid state reaction at 1 300 ℃ for 2 h. In order to study the theoretical mechanism affecting the emissivity, the phases structure of the material and the emission characteristics in near-infrared band were analyzed and characterized by XRD, FT-IR, SEM, XPS and Upward IntegratIRTM etc, the electronic structure was analyzed by first-principles calculation. The results show that the emissivity of the powder in the 1-5 μm band increases, but the absorption rate of the Cr single-doped sample increases little, while the Mg-Cr co-doped powder increases greatly, and the absorption rate in the near-infrared above 0.9. The reason is that the crystal is distorted after Cr single-doped, but the concentration of free carriers does not increase. After Mg-Cr co-doped, the distortion is intensified and more oxygen vacancies and small polarized molecules are formed, which enhance the free carriers absorbtion. The hybrid energy level that formed by orbitals of Cr 3d and O 2p causes the powder forbidden band width to be narrowed, the same as the Cr 3d orbital in the near-Fermi level conduction zone. Although Mg does not directly affect the band gap value, it indirectly changs the morphology of B-position elemens, and more small polarized molecules are produced. Therefore, comopared with the LafeO3 band gap value (3.817 eV), the Mg-Cr co-doped(0.109 eV) has the largest decrease, and the single-adoped(2.406 eV) secondly.