Abstract: The effect of Sm, Eu and Gd on electrical properties of a new class of polystalline ceramics based on TiO₂ was investigated. The content of added Sm, Eu and Gd is 2% (atomic ratio), while that of the other addition is always maintained at a constant value. The disks were sintered at 1380 ℃ for 4 h. It was found that Sm, Eu and Gd can reduce the voltage values (corresponding to 1 mA current) of TiO₂-based varistors effectively, but do not strongly influence the nonlinear values. The voltage values of the doped TiO₂-based varistors were 12.7 V (Sm doped), 14.7 V (Eu doped) and 16.1 V (Gd doped). Through impedance analysis, it can be found that those rare-earth ions have great influence on the dielectric properties; the single addition of Sm or Gd could attain very low dielectric constant, low dissipation factor and very high resistivity. Sm, Eu and Gd distribute surrounding the TiO₂ grains, but discontinuously.

Key words: Varistor, Rare- earth ions, Doping, Titania, Defect