Measurements and Simulation of Infrared Radiation Performance of LaAl0.67B0.33O3-δ(B=Mn/Ni)
Ca/Mn/Ni doped LaAlO3 was prepared by sol-gel method,and its infrared emission properties and change mechanism were investigated via XRD,XPS and IR,and its electronic energy band structure was simulated by CASTEP.It is concluded that the emissivity of LaAlO3 doped samples is enhanced in the near-infrared band,and the emissivity of La0.67Ca0.33Al0.67Ni0.33O3-δ in the 0.2-2.5 μm band is up to 0.9527.The mechanism of enhancement is that a large number of small polaritons Ni2+↔Ni3+are formed after Ca-Ni doping,and the concentration of electron-oxygen vacancies increases,which in turn promotes free carrier absorption;meanwhile,the doping of Ca-Ni results in a large distortion of the crystal,1.42 × 10-3(3.65 × 10-4 for LaAlO3),which intensifies the vibrational absorption.The minimum band gap of La0.67Ca0.33Al0.67Ni0.33O3.a is 0.334 eV(3.445 eV for LaAlO3).The small band gap facilitates the valence band electron leap,which in turn generates more electron-oxygen vacancy pairs and promotes the free carrier absorption.The band gap decreases as the conduction band of La0.67Ca033Al0.67Ni0.33O3-δ shifts to the lower energy region and the impurity energy level Ni 3d appears.The La0.67Ca0.33Al0.67Ni0.33O3-δ dielectric function peak and absorption coefficient peak are red-shifted thanks to the reduction of band gap.
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