High-pressure behaviour of synthetic weberite-type Mn2+2Sb5+2O7: an in situ single-crystal X-ray study.

An in situ high-pressure X-ray diffraction study has been carried out at room temperature up to 9.26 GPa on synthetic Mn2Sb2O7 having a weberite-3T structure. 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: V0 = 782.7(2), KT0 = 150(1) GPa. Unit-cell parameters decrease gradually as a function of pressure with a bulk modulus anisotropy scheme, with a being the softest direction. The overall mean polyhedral distances are quite constant, indicating a scarce compressibility of both the A and B polyhedra in the pressure range investigated. The compressional behaviour of Mn2Sb2O7 is compared with that shown by ingersonite, Ca3MnSb4O14, and synthetic orthorhombic Ca2Sb2O7.