Incorporation of Cd-Doping in SnO2

Tuning the electrical properties of materials by controlling their doping content has been utilized for decades in semiconducting oxides. Here, an atomistic view is successfully employed to obtain local information on the charge distribution and point defects in Cd-doped SnO2. We present a study that uses the time-differential perturbed gamma–gamma angular correlations (TDPAC) method in samples prepared by using a sol–gel approach. The hyperfine field parameters are presented as functions of the annealing temperature in pellet samples to show the evolution of incorporating Cd dopants into the crystal lattice. Additionally, the system was characterized with X-ray fluorescence, electron dispersive spectroscopy, and scanning electron microscopy after the probe nuclei 111In(111Cd) decayed. The TDPAC results reveal that the probe ions were incorporated into two different local environments of the SnO2 lattice at temperatures up to 973 K for cation substitutional sites.

Effect of Gd2O3 on the Electrical Properties of (Co, Nb)-Doped SnO2 Varistors

The effect of Gd2O3 on the electrical properties of (Co, Nb)-doped SnO2 varistors was investigated. It was found that the nonlinear coefficient presents a peak of α = 30 for the sample doped with 1.5mol% Gd2O3. The increase of the breakdown electrical field from 325V/mm to 1560V/mm with increasing Gd2O3 concentration is mainly attributed to the decrease of the grain size. The decrease of relative density and resistance of grain boundary indicate that Gd2O3 should be a two-sided dopant and the nonlinear coefficient peak was explained. To illustrate the grain-boundary barrier formation of (Gd, Co, Nb) doped SnO2 varistors, a modified defect barrier model was introduced, in which the negatively charged acceptors substituting for Sn ions should not be located at the grain interfaces instead at SnO2 lattice sites of depletion layers.