Depolarization experiments on space charges in concentrated solid solutions of NdF3 in SrF2

The influence of the defect concentration on the relaxation of space charges in Sr1-xNdxF2+x solid solutions has been investigated with the ionic-thermocurrent technique. A concentration domain of 0.004 up to 45 mol% has been used. As in the system Ba1-xLaxF2+x the space-charge relaxation band (high-temperature band) shifts to lower temperatures with increasing RF3 concentration. A percolation model has been used to explain these shifts. Most of the differences between the systems Sr1-xNdxF2+x and Ba1-xLaxF2+x are reducible to different dipolelike jumps supporting the charge transport: nearest-neighbor dipolelike jumps in Sr1-xNdxF2+x and next-nearest-neighbor dipolelike jumps in Ba1-xLaxF2+x. The charge transport may be interpreted qualitatively with a percolation mechanism.