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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。
La2CuO4 and La2-xMxCuO4-δ (M = Ca, Sr and Ba) crystals were prepared by sol-gel method. La2CuO4 and La2-xMxCuO4-δ (x = 0.1) powders were tested and characterized by X-ray diffraction, scanning electron microscopy and UV-Vis-NIR spectroscopy. The results show that single-phase La2CuO4 and La2-xMxCuO4-δ (M = Ca, Sr and Ba) can be obtained by calcination at 700 ℃ for 2 h, and all have orthorhombic crystal structure. The spectroscopic properties show that La2CuO4 and La2-xMxCuO4-δ compounds have a broad absorption in the UV-visible and near-infrared ranges. The band gaps of La2CuO4, La1.9Ca0.1CuO4-δ, La1.9Sr0.1CuO4-δ and La1.9Ba0.1CuO4-δ are 1.44, 1.57, 1.40 eV and 1.37 eV, respectively. Band gap changes are due to the different radius of the alkaline earth metal ions, resulting in the key of the mismatch caused by different effects.