TRANSPORT STUDIES OF LA1.92SR0.08CU1-XMXO4 (M=NI AND ZN) AND ND2-YCEYCUO4 UP TO ABOUT 900-K

Various transport quantities have been measured for La1.92Sr0.08Cu1-xMxO4 (M = Ni and Zn) and Nd2-yCeyCuO4 over a wide temperature region to study the crossover-like change of the electronic state previously found in high-T(c) oxides. The change shows a formation process of the anomalous low carrier concentration state near the Mott metal-insulator phase boundary. The Zn doping produces only a weak change of the T-dependence of the transport properties, except for electron localization effects at very low temperatures, while the Ni doping introduces a rather significant change of their T-dependence. Results of the measurements on Nd2-yCeyCuO4 have revealed that a rough relation of the electron-hole symmetry with respect to the ''half-filled'' Mott-insulating phase holds in the transport behaviors.