摘要：

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.

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