Difference in conductivity between LiD and LiH crystals

The LiD and LiH conductivities have been compared in the temperature range 300-900°K. In both (LiD and LiH) the conductivity curve ${log}_{10}\left(\sigma T\right)=f\left(\frac{1}{T}\right)$ shows three linear regions: (i) an intrinsic, (ii) a dissociation, and (iii) an association region. In all examined temperature ranges the conductivity values of LiD are smaller than those of LiH. The formation energy of Schottky defects is different in these two materials (2.40 and 2.33 eV, in LiD and LiH, respectively). Furthermore, the association energy of the ${\mathrm{Mg}}^{+2\mathrm{}}$-cation-vacancy complex is 0.76 eV in LiD and 0.84 eV in LiH; these values are unexpectedly much higher than those found in the alkali halides. Also large aggregation phenomena exist in crystals which have not undergone the usual thermal treatment.