Giant negative thermal expansion in ultrafine-grained Mn3(Cu1-xGex)N (x = 0.5) bulk

The advanced negative thermal expansion (NTE) properties of the ultrafine-grained Mn3(Cu1-xGex)N compound bulk have been reported. The developed preparation route has reduced the fabrication time by more than ten times in contrast to previous studies. As compared with the coarse-grained compound bulk, the NTE start temperature of the ultrafine Mn3(Cu1-x Gex)N (x = 0.5) bulk is reduced to 250 K, and the coefficient of negative thermal expansion (CNTE) reaches -23.7 x 10-6 K-1, which is remarkably improved. It is found that the nitrogen content in the starting manganese nitride also has significant effects on the NTE start temperature, operating temperature range and CNTE. (fast track communication)