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 Mn-3(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 Mn-3(Cu1-xGex)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.