Thermal stability and compressibility of bastnaesite

Bastnaesite (Ce0.50La0.25Nd0.20Pr0.05)CO3F is an interesting pattern family of (CO3)2− and F− co-existing phases, which is a meaningful sample to study the influence of multiple volatiles on minerals. Thermal stability of bastnaesite has been investigated by thermogravimetric experiment and in situ high-temperature Raman. The results demonstrate that bastnaesite undergoes a decarbonization transition at above 673 K. The isobaric-mode Gruneisen parameters range from 0.04 to 2.28. The compressibility of bastnaesite has been investigated by synchrotron radiation X-ray diffraction and Raman spectroscopy combined with diamond anvil cells up to 19.2 GPa at room temperature. Isothermal pressure–volume relationship of bastnaesite is fitted to the second-order Birch–Murnaghan equation of state with V0 = 430.87(3) A3, K0 = 118.35(1) GPa. Its axial compressibility presents anisotropic, attributed to the rigid (CO3)2− group parallel to c-axis. Its isothermal-mode Gruneisen parameters and intrinsic anharmonic-mode parameters range from 0.23 to 1.91 and− 3.5 × 10−5 K−1 to 0.82 × 10−5 K−1, respectively. The presence of F− can largely enhance the thermal stability and incompressibility of minerals.