Pressure induced reversal of the volume expansion caused by interstitial nitrogen in Nd2Fe17N3

Crystallographic properties of Nd2Fe17N3 have been investigated using powde r neutron diffraction techniques at pressures up to 7.3 GPa, With increasin g pressure, the unit cell volume of Nd2Fe17N3 decreases almost linearly at a rate of 6.1 Angstrom(3)/GPa without undergoing a phase transformation or expelling the interstitial nitrogen atoms. The observed rate of contraction corresponds to a bulk modulus of 1.4X10(11) N/m(2) for Nd2Fe17N3. The unit cell volume of Nd2Fe17N3 at 7.3 GPa is approximately equal to that of Nd2F e17 at atmospheric pressure. Even though the unit cell of Nd2Fe17 expands a nisotropically due to nitrogenation, contraction of the Nd2Fe17N3 unit cell under pressure appears to be isotropic with lattice parameters a and c dec reasing by approximately 1.8% as the sample pressure increases from ambient to 7.3 GPa. (C) 1998 American Institute of Physics. [S0021-8979(98)35911-3 ].