Thermal expansion of fluorapophyllite KCa4[Si8O20]F center dot 8H(2)O in the 323-473 K range from X-ray powder diffraction data

摘要

Thermal expansion of fluorapophyllite KCa4[Si8O20]F center dot 8H(2)O has been analysed in the 323-473 K thermal range by laboratory parallel-beam transmission X-ray powder diffraction. Thermal expansion is markedly anisotropic as indicated by (alpha) over bar (alpha) of 2.205(13).10(-5) and (alpha) over bar (c) of 4.98(15).10(-6). Very minor variations of relevant bond distances are observed during heating. Anisotropy of thermal expansion has been attributed to the fact that the mean plane passing through Ca,O(4),K has a prevalent component along the (001).