La_(1-x)CaxAl_(1-y)B_(y)O_(3-δ)(B=Mn/Ni)的红外辐射性能测试与模拟

Measurements and Simulation of Infrared Radiation Performance of La_(1-x)CaxAl_(1-y)B_(y)O_(3-δ)(B=Mn/Ni)

采用溶胶凝胶法制备了Ca/Mn/Ni掺杂LaAlO_(3),借助X射线衍射(XRD),X射线光电子能谱(XPS)以及红外辐射(IR)研究了其红外发射性能及改变机理,同时运用CASTEP模拟了其电子能带结构。研究结果表明:掺杂样品相比LaAlO_(3)在近红外波段发射率都有较大提升,La_(0.67)Ca_(0.33)Al_(0.67)Ni_(0.33)O_(3-δ)在0.2~2.5μm段的发射率可达0.9527。提升的机制为:掺Ca-Ni后形成了大量小极化子Ni2+?Ni^(3+),且电子-氧空位的浓度增加,进而促进了自由载流子吸收;同时,掺Ca-Ni时,晶体发生了较大畸变,为1.42×10^(-3)(LaAlO_(3)为3.65×10^(-4)),强化了振动吸收。La_(0.67)Ca_(0.33)Al_(0.67)Ni_(0.33)O_(3-δ)带隙最小,为0.334eV(LaAlO_(3)的为3.445eV)。小带隙有利于价带电子跃迁,进而产生更多的电子-氧空位对,促进自由载流子吸收。La_(0.67)Ca_(0.33)Al_(0.67)Ni_(0.33)O_(3-δ)导带向低能区转移并出现了杂质能级Ni3d,因此带隙减小。得益于带隙的减小,La_(0.67)Ca_(0.33)Al_(0.67)Ni_(0.33)O_(3-δ)介电函数虚部峰以及吸收系数峰均红移。

Ca/Mn/Ni doped LaAlO_(3)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 LaAlO_(3)doped samples is enhanced in the near-infrared band,and the emissivity of La0.67 Ca0.33 Al0.67 Ni0.33 O_(3-δ)in the 0.2‒2.5μm band is up to 0.9527.The mechanism of enhancement is that a large number of small polaritons Ni2+↔Ni^(3+)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 LaAlO_(3)),which intensifies the vibrational absorption.The minimum band gap of La0.67 Ca0.33 Al0.67 Ni0.33 O_(3-δ)is 0.334 eV(3.445 eV for LaAlO_(3)).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 La0.67 Ca0.33 Al0.67 Ni0.33 O_(3-δ)shifts to the lower energy region and the impurity energy level Ni 3d appears.The La0.67 Ca0.33 Al0.67 Ni0.33 O_(3-δ)dielectric function peak and absorption coefficient peak are red-shifted thanks to the reduction of band gap.