ISSN:
1600-5740
Source:
Crystallography Journals Online : IUCR Backfile Archive 1948-2001
Topics:
Chemistry and Pharmacology
,
Geosciences
,
Physics
Notes:
The lattice dynamics of Na4TiP2O9 (tetrasodium titanium diphosphorus nonaoxide, NTP) and Na4.5FeP2O8(O,F) (nonasodium diiron tetraphosphorus difluoride octadecaoxide, NFP) crystals, which are superionic conductors with Na+-ion conductivity, were studied under high pressures. Lattice constants as a function of hydrostatic pressure were measured on a four-circle diffractometer using a high-pressure cell with diamond anvils. At 1.78 \pm 0.15 GPa NTP undergoes a reversible phase transition from the modulated monoclinic (pseudo-orthorhombic) modification which is stable under atmospheric conditions. A similar phase transition in NTP is observed at 523 K. For NFP, it may be assumed that at least three phase transitions occur when the pressure increases from atmospheric to 12 GPa, at 1.39\pm0.08, 4.52 \pm0.32, and 6.02\pm0.02 GPa, as concluded from the change in the unit-cell parameters and in the color of the crystals: the color changes from ginger (dark orange) to pink at \sim1.5–2.0 GPa pressure and to violet at \sim6.0 GPa.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1107/S0108768198011239
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