X-ray diffraction study of calcium-lead fluorapatite solid solution at high pressure: the composition dependence of the bulk modulus and its pressure derivative

摘要

The compression behavior of a natural fluorapatite has been investigated to about 29.2 GPa at 300K using in situ angle-dispersive X-ray diffraction and a diamond anvil cell at High Pressure Experiment Station, Beijing Synchrotron Radiation Facility (BSRF). The unit-cell parameters and volume decreased systematically with increasing pressure, and the isothermal equation of state was determined. The values of V_0, K_0, and K~'_0 refined with a third-order Birch-Murnaghan equation of state are V_0= 559.7 ± 0.8 ?3 K_0 = 75 ± 5 GPa. and K~'_0 = 5.6 ± 0.7. Furthermore, we obtained that the axial compressibilities of the natural fluorapatite [3.97(8) × 10~(-3) GPa~(-1) and 3.12(6) ×10~(-3)GPa~(-1) for the a- and c-axis, respectively]. In addition, combining with previous results, the compositional dependence of the bulk modulus and its pressure derivative are discussed.