High-pressure behavior of the synthetic Ca2Sb2O7 weberite-type compound

An in situ high-pressure X-ray diffraction study has been carried out at room temperature up to 9.23 GPa on a crystal of Ca2Sb2O7 having a weberite-20 structure synthesized by solid-state reaction. A 2nd-order Birch-Murnaghan Equation of State (EoS) was used to refine the pressure-volume data. The refinement of the unit-cell volume and of the isothermal bulk modulus at room pressure leads to: V-0 = 555.8 (1), K-T0 = 154.6 (9) GPa. Unit-cell parameters decrease gradually as a function of pressure with a bulk modulus anisotropy scheme K-a0 > K-b0 > K-c0, with c being the softest direction. The compressional behavior of Ca2Sb2O7 is compared with that shown by ingersonite, Ca3MnSb4O14, a mineral showing a weberite-3T structure. (C) 2011 Elsevier Masson SAS