High-pressure and high-temperature X-ray diffraction studies of scheelite BaWO4

R. Lacomba-Peralesa (1) , D. Martínez-García (1) , D. Errandonea (1) , Y. Le Godec (2) , J. Philippe (2) , Guillaume Morard (2)

1 ICMUV - Institut Universitari de Ciencia dels Materials
2 IMPMC - Institut de minéralogie et de physique des milieux condensés

We carried out high-pressure (HP) and high-temperature (HT) in situ ADXRD synchrotron measurements in barium tungstate (BaWO4 ) up to 7.5 GPa and 800 K. Coexistence of the scheelite and fergusonite structures was found beyond 7 GPa, both at room temperature and HT, suggesting a polymorphism zone in the P –T phase diagram. The experiments are complemented by thermodynamic calculations within the quasi-harmonic approximation. At ambient pressure, a volume thermal expansivity of 9.5 × 10− 6 K−1 was obtained for scheelite BaWO4 . At HP, the thermal expansivity of the fergusonite doubles that of scheelite. Theoretical equation of state curves at HP and HT are also presented.

Mots clés: scheelite; fergusonite; high pressure; high temperature; X-ray diffraction; EOS

Domaines: Autre [cond-mat.other]

R. Lacomba-Peralesa, D. Martínez-García, D. Errandonea, Y. Le Godec, J. Philippe, et al.. High-pressure and high-temperature X-ray diffraction studies of scheelite BaWO4. High Pressure Research, 2009, 29, pp.76-82. ⟨10.1080/08957950802417792⟩. ⟨hal-00441590⟩