ELECTRONIC TRANSPORT-PROPERTIES OF HOLE-DOPED SR1+XLA1-XCRO4+DELTA

Polycrystalline bodies of Sr1+xLa1-xCrO4+delta (0 less than or equal to x less than or equal to 0.3) with a K2NiF4 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 esp[(-T-0/T)(alpha)] (alpha=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 nonmetallic 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 x 10(8) K, This was larger by two orders of magnitude than reported values in La2CuO4 which was insulating between room temperature and 2 K. Based on the VRH regime, the larger To 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 To and the density of states in the vicinity of the Fermi energy.