Patent ID: 7632480

Claim:
A thermal expansion inhibitor, which comprises manganese nitride crystals having a composition of the following formula (2), and which has negative thermal expansion over an at least 10° C. range: Mn 3+x2 A 21y2 A 22 1−x2−y2 N Formula (2) wherein A 21 is one kind of atom selected from the group consisting of Co, Ni, Cu, Zn, Ga, Rh, Pd, Ag, Cd and In, A 22 is one or more kinds of atoms selected from the group consisting of Al, Si, Sc, and atoms of Groups 4A to 5B of the 4th to 6th Periods of the Periodic Table that are not Mn, in which A 21 and A 22 are not the same; 0≦x2<1; 0<y2<1; and 1>x2+y2; wherein up to 20% of N in the crystal structure may be substituted with B, C, O, P or S.