| Apatite group minerals are widely distributed in the earth’s crust.They contain unique channel structures and are rich in isomorphous substitution.This dissertation studied two natural apatite crystals from different areas by conventional gemmological methods,infrared diffuse reflectance spectroscopy（IR）and X ray fluorescence spectrometry（XRF）.IR spectra show that both samples have characteristic absorption peaks which can be assigned to[PO4]3-.According to the characteristic peaks,the main components and types of the two samples were determined.The sample from Brazil is Fluor apatite and the sample from Sichuan is Fluor-Chlorapatite.In situ high-pressure experiments were carried out using a Diamond Anvil Cell（DAC）combined with synchrotron radiation facility.The achieved maximum pressure of fluor apatite from Brazil is 11.40 GPa while the maximum of Fluor-Chlorapatite being 11.96 GPa.The cell parameters of a,c and V reduce with the increasement of pressure,and have linear relationship with the pressure.The axial compressibility of Fluorapatite isβa=-3.06×10-3 GPa-1,βc=-2.36×10-3 GPa-1,andβa=-2.62×10-3 GPa-1,βc=-2.53×10-3 GPa-1 for Fluor-Chlorapatite.EOSfit software is used to fit the volume-pressure data with the three order Birch-Murnaghan equation of state（Birch,1947）to obtain the initial volume,bulk modulus and other information.The obtained parameters show as follows,V0=524.4（9）?3,K0=90.1（1）GPa,K’=4.8（3）for Fluor apatite from Brazil and V0=541.7（6）?3,K0=93.9（7）GPa,K’=5.6（8）for Fluor-chlorapatite.In addition,the high temperature XRD was used to test the structural stability of Sichuan apatite.The experimental temperature ranges from 27 to 1100℃.The a,c and V expand with increasing temperature and are linearly related to temperature.The thermal expansion coefficient of the sample is?a/a=8.82×10-6℃-1,?c/c=8.52×10-6℃-1,V/V0=2.64×10-5℃-1. |
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