Effect of pyrochemical waste loading on the heat capacity of Sr10(PO4)6Cl2 and its glass-bonded composites measured by drop calorimetry

First-principles study on structural, electronic, vibrational and thermodynamic properties of Sr10(PO4)6X2(X = F, Cl, Br)

“…All our studies are carried out at P ¼ 0 GPa and hence PV ¼ 0, as a result the H ¼ E. It is found the calculated S, H À H 298 and C P of Sr-ClAP exhibit reasonable agreement with the experimental values. 35,48,49 So our predicted thermodynamic properties for Sr 10 (PO 4 ) 6 X 2 (X ¼ F, Cl, Br) are reliable. There are no experimental or theoretical works exploring the thermodynamic properties of crystal Sr-FAP and Sr-BrAP for comparison with the present data, we hope our predicted results can give a reference for the future study.…”

“…[31][32][33][34] Thirdly, as the member of apatite family, Sr 10 (PO 4 ) 6 X 2 (X ¼ F, Cl, Br) are considered to be suitable for nuclear waste storage, such as the glass encapsulated Sr 10 (PO 4 ) 6 Cl 2 (Sr-ClAP) can immobilize most of the radwaste elements in the composite matrix. 35 There are some investigations have been carried on the crystal Sr 10 (PO 4 ) 6 X 2 (X ¼ F, Cl, Br). The crystal structures of Sr 10 (PO 4 ) 6 X 2 (X ¼ F, Cl, Br) were determined with X-ray diffraction.…”

“…43,44 The results indicate Sr-FAP and Sr-ClAP have large thermal expansion coefficient and there are not any phase transformations for Sr-FAP and Sr-ClAP in temperature interval 298-1723 K. The formation enthalpies of Sr-FAP and Sr-ClAP were given at the standard of 298 K and 1 bar. [45][46][47] Specially, the heat capacity and enthalpy increments of Sr-ClAP were measured by Hrudananda Jena et al 35,48,49 Furthermore, the thermodynamics functions of Sr-ClAP were computed by least-squares tting method from the measured enthalpy increments and compared with the Ca 10 (PO 4 ) 6 Cl 2 and Ba 10 (PO 4 ) 6 Cl 2 , which indicate that the specic heat capacity of the alkaline earth chloroapatites increases in the order barium < strontium < calcium and the alkaline earth chloroapatites can withstand decay heat of the radio nuclides without decomposition or degradation. 49 Theoretically, the electronic properties and elastic constants of Sr 10 (PO 4 ) 6 X 2 (X ¼ F, Cl, Br) were calculated using density functional theory (DFT) with the generalized gradient approximation (GGA) functional.…”