Electrical conduction in superconductive Nd2−xCexCuO4−y at high temperatures

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Abstract
The temperature dependence of electrical resistivity of Nd2−xCexCuO4−y (x = 0.0, 0.1, 0.15, 0.18) was measured at oxygen partial pressures of 2.08 × 10−1 1.8 × 10−2, 8.1 × 10−4, and 3.3 × 10−6 atm. The oxygen-partial-pressure dependence of resistivity indicated that the charge carriers in Nd2−xCexCuO4−y were electrons. According to the resistivity data of these compounds at temperatures above 770 K, Ce doping affected the relation between the oxygen deficiency and oxygen partial pressure in Nd2CuO4−y: the doping of Ce worked to hinder the formation of oxygen vacancies in the lattice. Moreover, the carrier density after Ce doping was found to be much less than the value anticipated from the amount of the dopant. This suggested that not all the doped Ce ions worked as donors. That is, the relative amount of Ce3+ ions compared to that of Ce4+ ions increased as the total amount of the doped Ce ions increased.