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Article Dans Une Revue Journal of Physical Chemistry C Année : 2015

AlPO4-54-AlPO4-8 Structural Phase Transition and Amorphization under High Pressure

Résumé

Microporous AlPO4-54, which exhibits the largest pores among zeolites and aluminophosphates with a diameter of 12.7 Å, was investigated at high pressure by X-ray powder diffraction (XRD), mid- and far-infrared (IR) spectroscopy in diamond anvil cells. The material undergoes a phase transition beginning around 0.8 GPa. The amount of AlPO4-8 gradually increases with pressure and the phase transition is complete between 2 and 3 GPa. The closure of the (P—O—Al) angle destabilizes the structure of AlPO4-54, which drives the transition to AlPO4-8. The pressure-induced phase transformation of AlPO4-54 to AlPO4-8 is associated with a symmetry reduction from hexagonal to orthorhombic and with a change in the unidirectional ring channel parallel to the c-axes from 18 to 14 AlO4 and PO4 tetrahedra. An abrupt decrease along the b direction is linked to the formation of 4 new rings of 6 tetrahedra with significant structural reorganization. The transition is followed by irreversible amorphization beginning around 3.5 GPa due to the collapse of the pores. The amorphization of AlPO4-8 was detected from the disappearance of the XRD lines, abrupt shifts, and strong broadening of the mid-IR modes, and by changes in the pressure dependence of the mid- and far-IR modes, indicating a lower compressibility for the more dense amorphous form. Far-IR spectra indicate that the new amorphous form retains the local structure of AlPO4-8.

Domaines

Matériaux
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Dates et versions

hal-01202111 , version 1 (18-09-2015)

Identifiants

Citer

Frederico Alabarse, Jean-Blaise Brubach, Pascale Roy, Abel Haidoux, Claire Levelut, et al.. AlPO4-54-AlPO4-8 Structural Phase Transition and Amorphization under High Pressure. Journal of Physical Chemistry C, 2015, 119 (14), pp.7771-7779. ⟨10.1021/acs.jpcc.5b00318⟩. ⟨hal-01202111⟩
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