Preparation and Negative Thermal Expansion Research in Anti-Perovskite Ga_(1-x)N_(0.8)Mn_(3+x)( 0

Heat bilges cold shrinkalways lead to stress concentration at the grain boundary,vacancy and so on,and then cause thermal fatigue and mechanical fatigue shorten,which reduce the materials' reliability and short their service life. In recent years,anti-perovskite manganese nitrides with similar crystal structure of cubic structure of perovskite manganese oxides have attracted much attention because of the negative thermal expansion( NTE) they display,and the good thermal conductivity,electrical conductivity and so forth. A new series of anti-perovskite manganese nitrides Ga1- xN0. 8Mn3 + x( 0 x≤3) were prepared using solid-state reaction method. In the present work,the negative thermal expansion( NTE) and the electrical transport were studied. With the increment of Mn-doping level,the temperature span of the magnetovolume effect not only is broadened but also is shifted toward lower temperatures. For the sample of x = 0. 2 and x = 0. 25,the temperature span of NTE is 294 ~ 339 K and 255 ~ 309 K,and the corresponding coefficient of linear thermal expansion is- 51 ppm / K and- 42 ppm / K,respectively. An abnormal behavior of resistivity was observed,in line with the contraction of the lattice. The NTE behaviors may be attributed to the disturbance of the Γ5gantiferromagnetic ground state by partially substituting the Ga atoms with Mn.