Low thermal expansion behavior and electrical conductivity of Mn_3(Cu_(0.5)Si_xGe_(0.5-x))N at low temperatures

摘要

Anti-perovskite manganese nitrides with the general formula Mn_3(Cu_(0.5)Si_xGe_(0.5-x))N (x = 0.05, 0.1, 0.15, 0.2) were fabricated by mechanical ball milling followed by solid state sintering. The temperature dependence of thermal expansions, magnetic properties and electrical conductivities were investigated in the temperature range of 77-300 K. The results show that the operation-temperature window of negative thermal expansion (NTE) shifts to lower temperature and the magnitude of NTE becomes smaller with increasing Si content. Very low average coefficients of thermal expansion of 1.3 x 10~6 K_1 and 1.65 X 10~(-6) K~(-1) were observed in Mn_3(Cu_(0.5)Si_(0.1)Ge_(0.4))N and Mn_3(Cu_(0.5)Si_(0.15)Ge_(0.35))N within the temperature range of 77-300 K, respectively. In addition, the electrical conductivities of all the samples are in the range of 2.5-3.5 X 10~5 (ohm m)~(-1).