Thermal expansion of troilite and pyrrhotite determined by in situ cooling (873 to 373 K) neutron powder diffraction measurements

摘要

The thermal expansion coefficients for natural troilite, FeS, Ni-rich pyrrhotite, Fe_0.84Ni_0.11S, and Ni-poor pyrrhotite, Fe_0.87Ni_0.02S, were measured during cooling by in situ neutron powder diffraction over the temperature range 873–373 K. Between 873 and 573 K, the mean thermal expansion coefficients for the three compositions are 7.4(3) x 10–5 {FeS}, 8.0(4) x 10–5 {Fe_0.84Ni_0.11S} and 8.5(4)610–5 K–1 {Fe_0.87Ni_0.02S}. Below 573 down to 373 K, the first two increase considerably to 14.1(7) x 10–5 {FeS} and 9.3(5) x 10–5 {Fe_0.84Ni_0.11S} while the latter sample shows no significant variation, 8.4(5) x 10–5 K–1. Below 573 K, the thermal expansion is highly anisotropic, with a/100 K–1 ranging from 0.89(9)% {FeS} to 0.48(12)% {Fe_0.87Ni_0.02S} while c/100 K–1 ranges from –0.39(11)% {FeS} to –0.13(2)% {Fe_0.87Ni_0.02S}.