Effects of Nd, Sm, Gd, Dy, Er dopant on electrical properties of BaTiO₃ ceramics

BaTiO₃ ceramics doped with various quantities of Nd₂O₃, Sm₂O₃, Gd₂O₃, Dy₂O₃ and Er₂O₃ were prepared respectively (the adulterate concentrations were 0.001, 0.002, 0.003, 0.005, 0.007 mol fraction) through a sol-gel method and their electrical properties were researched. It is found that each adulteration of Nd₂O₃, Sm₂O₃, Gd₂O₃, Dy₂O₃ and Er₂O₃, Dy₂O₃, and Er₂O₃ all can make the resistivity of BaTiO₃ ceramics decline, especially Sm₂O₃ and Gd₂O₃. When the addition of Sm₂O₃ is 0.001 mol, the resistivity is the smallest, declining from 4.0×10¹² to 6.5×10³ Ω·m, and each different kind of rare earth exhibits different regularity. The grain resistance of BaTiO₃ ceramics doped with Sm₂O₃ or Gd₂O₃ exhibits a NTC effect, at the same time the grain boundary resistance has a PTC effect, and the grain boundary resistance is much larger than the grain resistance, so the PTC effects of BaTiO₃ ceramics doped with Sm₂O₃ or Gd₂O₃ originate from the grain boundary. The additions of Nd₂O₃, Gd₂O₃ or Er₂O₃ make the dielectric constant and the dielectric loss of BaTiO₃ ceramics change evidently, especially Nd₂O₃. The dielectric constant is larger than that of pure Ba-TiO₃ ceramics, on the other hand, the dielectric loss is much lower, which is useful in capacitor fields.