We investigated the high-pressure behaviour of Fe3+-bearing hydrous phase-X, (K1.307Na0.015)(Mg1.504Fe3+0.373 Al0.053Ti0.0044 )Si2O7H0.36, up to 34 GPa at room temperature by synchrotron X-ray powder diffraction. The lattice parameters behave anisotropically, with the  direction stiffer than . In the 10-4 to 22 GPa pressure range, the axial bulk moduli are K0a = 112(3) GPa and K0 = 4, and K0c = 158(2) GPa and K0 = 4, and the anisotropy of the lattice parameters is b0c:b0a = 0.71:1.The cell volumes are fitted by a second-order Birch–Murnaghan equation of state giving a bulk modulus of K0 = 127(1) GPa and K0 = 4 in the same pressure range. After 22 GPa, a discontinuity in volume and lattice parameters can be recognized. Sample did not become amorphous up to 34 GPa. The coupled substitution K , Mg =  , Fe3+ has only a limited influence on the bulk modulus and structural stability of phase-X.
Equation of state of Fe3+-bearing phase-X / Nazzareni, Sabrina; Comodi, Paola; L., Bindi; G., Garbarino; A., Bobrov. - In: PHYSICS AND CHEMISTRY OF MINERALS. - ISSN 0342-1791. - 39 / 2012:7(2012), pp. 553-559. [10.1007/s00269-012-0511-2]