A neutron powder investigation of the structure of KCaCO3F at various temperatures

The structure of KCaCO3F is reinvestigated to unambiguously determine the K and Ca sites by neutron powder diffraction. The powder neutron diffractions at temperatures (295 K, 373 K, 473 K, 573 K and 673 K) are also performed to reveal the thermal expansions for this compound. No structural transition in this compound is found in the experimental temperature range. The Rietveld refinements indicate that the unit cell parameters and the cell volume of the compound increase linearly with the increasing temperature. Large anisotropic thermal expansions are found in this compound. The thermal expansion coefficient along a (b) axis is over two times as large as that parallel to the c-axis. The possible reasons for the large anisotropic thermal expansions are briefly discussed.