Discovery of negative thermal expansion with giant thermal hysteresis in Fe₃NiB_x

Negative thermal expansion (NTE) behavior with giant thermal hysteresis exceeding 450 K has been observed in Fe₃NiB_x. This behavior is desirable in the field of pipe joint or encapsulation. The temperature dependent X-ray diffraction and magnetization indicate that NTE behavior with giant thermal hysteresis is related to crystal structure transition between face-centered cubic (fcc) and body-centered cubic (bcc), but not to the magnetic transition. The introduction of boron can reduce the NTE temperature range and stabilize the high temperature fcc phase. Therefore, we can obtain the NTE behavior below room temperature during cooling process, which is important for the practical application.