ホールドープしたSr_<1+χ>La_<1-χ>CrO_<4+δ>の電子伝導性

概要

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Polycrystalline bodies of Sr_<1+χ>La_<1-χ>CrO_<4+δ>(0≤χ≤0.3)with a K_2NiF_4 structure were prepared and the temperature dependence of the electrical conductivity and Seebeck voltage at room temperature were measured. The temperature dependence of conductivity followed a functional form of exp[(-T_0/T)^α](α=1/3 or 1/4), which was characteristic of two-or three-dimensional variable-range hopping(VRH)model. The hopping conductivity showed that the crystal was non-metallic because the electronic states at the Fermi energy were localized. Values of T_0 in the three-dimensional VRH regime were in the range of 1-5×10^8 K. This was larger by two orders of magnitude than reported values in La_2CuO_4 which was insulating between room temperature and 2 K. Based on the VRH regime, the larger T_0 values were considered to be caused by the smaller localization radius of impurity states. All the samples were demonstrated to have a positive Seebeck coefficient. Further, the coefficient decreased with increasing doping level. The composition dependence of the Seebeck coefficient was discussed in relation to the changes with compositions in T_0 and the density of states in the vicinity of the Fermi energy.
社団法人日本セラミックス協会の論文
1995-11-01