溶胶凝胶法制备的La2–xMxCuO4–δ晶体的UV–Vis–NIR光学性质（英文）

采用溶胶–凝胶法制备了La2CuO4和La2–xMxCuO4–δ(M=Ca、Sr和Ba)晶体。通过X射线衍射、扫描电子显微镜和紫外–可见–近红外光谱对La2CuO4和La2–xMxCuO4–δ(x=0.1)粉体进行了测试和表征。结果表明,700℃煅烧2 h,可以获得单相La2CuO4和La2–xMxCuO4–δ(M=Ca、Sr和Ba),且均为正交晶型结构。光谱性质表明,La2CuO4和La2–xMxCuO4–δ系化合物在紫外–可见和近红外范围都有较宽的吸收。La2CuO4、La1.9Ca0.1CuO4–δ、La1.9Sr0.1CuO4–δ和La1.9Ba0.1CuO4–δ的带隙分别为1.44、1.57、1.40 eV和1.37 eV。带隙的变化是由于碱土金属离子的半径不同,造成对键的不匹配性的影响不同而引起的。

Optical Properties in the UV–Vis–NIR Region of La2-xMxCuO4-δ Crystallites Synthesized by Sol–Gel Process

The La2CuO4 and La2–xMxCuO4–δ(M = Ca,Sr and Ba) crystallites were prepared via a sol–gel process.The as-prepared La2CuO4 and La2–xMxCuO4–δ crystallites were characterized by X-ray diffraction,scanning electron microscope and ultravio-let–visible–near infrared(UV–Vis–NIR) spectroscopy.The results show that the pure La2CuO4 and La2–xMxCuO4–δ(x = 0.1) crystal-lites can be obtained after the calcination at 700 ℃ for 2 h,and the samples exhibit an orthogonal crystal structure.The La2CuO4 and La2–xMxCuO4–δ both had a broad absorption in the UV–Vis region and the NIR region,and the band gaps of La2CuO4,La1.9Ca0.1CuO4–δ,La1.9Sr0.1CuO4–δ and La1.9Ba0.1CuO4–δ were 1.44,1.57,1.40 and 1.37 eV,respectively.The variation of the band gap was attributed to the different radii of alkaline earth ions,having an effect on the bond-mismatch that caused the corresponding changes.