Structural Characters and the Conductivity of Nd2-xCexCuO4 Samples prepared under Atmosphere and High Pressure

Samples of Nd2-xCexCuO4 have been synthesized by using atmosphere pressure-high temperature (AT) and high pressure-high temperature (HP) methods. The structural characters and electrical conductivity of the samples prepared by the two different methods have been studied. The sample synthesized by HP (1.7 GPa, 800 ℃, 10 min) has a tetragonal structure (T' phase), similar to that of the samples sintered by AP (1 000 ℃, 10 h), but their crystal parameter, c, varies in a different manner as the Ce4+ doping content, x, changes. The parameter c for HP products remains basically constant as the doping content x increases, whereas the parameter c for the AP products decreases obviously as x increases. Both samples prepared by AP and HP methods exhibit semiconducting properties in varying degrees under liquid nitrogen temperatures. The electrical conductivity of the HP samples, quenched at high temperature, is superior to that of AP samples. Experiments show that high pressure is beneficial to reduce the synthesis temperature, to shorten the reactive time of solid state reaction and, particularly, to improve the electrical conductivity of the samples due to the reduction role of high pressure.