The Dy2Ti2O7 oxide with high-density defects has been prepared by arc melting,showing a metallic black,which crystallizes in a cubic pyrochlore structure(space group Fd-3m,No.227)with a lattice parameter a=1.013 33(3)nm.There exist high-density defects,such as the cation anti-site occupation TiDy with the occu-pancy of 10.7％and titanium vacancies VTi.The distortion of[DyO8]cubic coordination is weakened and the dis-tortion of[TiO6]octahedron is enhanced,resulting in a new Raman peak at 139 cm-1.Its band gap is as large as Eg=3.50 eV,smaller by～0.3 eV than Eg～3.8 eV of the conventional samples.In the range of 1.0～3.4 eV,the transition between the 4f levels of Dy3+results in a broad light absorption peak.Due to the presence of Dy-poor characteristic,the spontaneous magnetic moment of Dy2Ti2O7 is as large as 4.8 μB/Dy at 2 K which is somewhat smaller than～5.0 μB/Dy of the conventional samples,accelerating the flipping process of Dy3+spins near 16 K.The resistivity measurement shows that Dy2Ti2O7 is a semiconductor with the thermal activation energy Ea=346.9 meV.
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