Compressibility of strontium orthophosphate Sr3(PO4)2 at high pressure

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 Å 3 , an isothermal bulk modulus of K T = 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).