Compressibility of strontium orthophosphate Sr_3(PO_4)_2 at high pressure

摘要

High pressure in situ synchrotron X-ray diffraction experiment of strontium orthophosphate Sr_3(PO_4)_2 has been carried out to 20.0 GPa at room temperature using multianvil apparatus. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields a volume of V_0 = 498.0 ± 0.1 ?~3, an isothermal bulk modulus of KT = 89.5 ± 1.7 GPa, and first pressure derivative of K_T′ = 6.57 ± 0.34. If K_T′ is fixed at 4, K_T is obtained as 104.4 ± 1.2 GPa. Analysis of axial compressible modulus shows that the a-axis (K_a = 79.6 ± 3.2 GPa) is more compressible than the c-axis (K_c = 116.4 ± 4.3 GPa). Based on the high pressure Raman spectroscopic results, the mode Grüneisen parameters are determined and the average mode Grüneisen parameter of PO_4 vibrations of Sr_3(PO_4)_2 is calculated to be 0.30(2).