Sn-Doped Mn3GaN Negative Thermal Expansion Material for Space Applications

The anti-perovskite manganese nitrides with the general formula Mn3Ga1-xSnxN (x=0, 0.1, 0.2, 0.3, 0.4) were fabricated by mechanical ball milling followed by spark plasma sintering (SPS). The temperature dependence of thermal expansion, thermal conductivity and mechanical properties were investigated. The results show that the negative thermal expansion (NTE) operation-temperature window shifts toward higher temperature with increasing of Sn concentration. Typically, the linear NTE coefficient of the Mn3Ga0.9Sn0.1N compound reaches as much as −27.5×10−6 K−1, with an operation-temperature window of 59 K from 279 to 338 K. In addition, the coefficient of thermal expansion (CTE) of Mn3Ga0.6Sn0.4N is very low in the temperature range of 363∼400 K. The value of thermal conductivity of this material is about 3.2 W·(m·K)−1 around room temperature. Compression test indicates that the compressive strength is about 210 MPa. This NTE material may possibly be exploited to design the critical components for space applications.