The Donor Level of V4+ and the Metal-Nonmetal Transition in SrTi1-xVxO3

The electrical conductivity of single crystalline SrTi1-x V x O3 (0.1≦x≦1) was measured down to 4.2 K. The depth of the donor level of V4+ in SrTiO3 was about 0.6 eV. The metal-nonmetal transition occurred at x≃0.6 with σ≃280 Ω-1 cm-1 and the conductivity increased with x up to about 2×104 Ω-1 cm-1 at x=1. In the semiconducting region of x<0.6, the electrical conduction was of the activation type with a constant activation energy in the higher temperature range and with a decreasing activation energy in the lower temperature range. The temperature dependence of the electrical conductivity can be explained by hopping conduction in the donor band. The deep donor level, the metal-nonmetal transition at extremely large concentrations of donors and other results can be systematically explained by assuming the local Jahn-Teller distortion around V4+ ions.