Abstract:

Cr³⁺-Fe³⁺ co-doped lanthanum aluminate was prepared using La₂O₃ powder,Al₂O₃ powder,Cr₂O₃ powder,and Fe₂O₃ powder as raw materials.The ingredients were blended stoichiometrically according to LaAl_1-x-yCr_xFe_yO₃(x=y=0,0.1,0.2,0.25),ball milled,dried,prefired at 1 200 ℃,ball milled again,molded and sintered at 1 600 ℃ for 2 h.The doped LaAlO₃ was characterized by XRD,XPS and IR.The results show that all the doped products are perovskite structural compounds.The near-infrared radiation performance of the Cr³⁺-Fe³⁺ co-doped samples is greatly improved compared with the undoped ones.The infrared emissivity of the sample LaAl_0.5Cr_0.25Fe_0.25O₃ in the 0.76-2.5 μm waveband increases from 0.236 to 0.83.The increasing mechanism of the infrared emissivity is considered as follows.After co-doping,Cr ³⁺-Fe³⁺ forms Fe³⁺$\leftrightarrow$Fe⁴⁺ small polaron with a transition activation energy of only 0.1 eV,introducing the impurity energy levels corresponding to Cr⁵⁺ and Cr⁶⁺.Thus the impurity absorption and free carriers absorption are enhanced,improving the emissivity in the near-infrared waveband of the material.

Key words: lanthanum aluminate, infrared emissivity, B site doping, ceramic material

摘要：

以La₂O₃粉、Al₂O₃粉、Cr₂O₃粉、Fe₂O₃粉为原料,按照LaAl_1-x-yCr_xFe_yO₃(x=y=0,0.1,0.2,0.25)的化学计量比配料,依次经球磨、烘干、在1 200 ℃预烧、再球磨、成型、1 600 ℃保温2 h烧结后,制备了Cr³⁺-Fe³⁺共掺杂铝酸镧材料,然后利用XRD、XPS、IR等手段进行分析表征。结果表明:掺杂后产物均为钙钛矿结构化合物。Cr³⁺-Fe³⁺共掺杂试样在近红外波段的辐射性较未掺杂的LaAlO₃大幅提高,试样LaAl_0.5Cr_0.25Fe_0.25O₃在0.76~2.5 μm波段的红外发射率从0.236提高到0.83。红外发射率提高的机制在于:Cr ³⁺-Fe³⁺共掺杂后形成了跃迁激活能仅为0.1 eV的Fe³⁺$\leftrightarrow$Fe⁴⁺小极化子,并且带隙中引入了对应于Cr⁵⁺和Cr⁶⁺的杂质能级,增强了杂质吸收和自由载流子吸收,从而提高了材料在近红外的发射率。

关键词: 铝酸镧, 红外发射率, B位掺杂, 陶瓷材料