J M Posse et al 2011 J. Phys.: Condens. Matter 23 215401 doi:10.1088/0953-8984/23/21/215401
J M Posse, K Friese and A Grzechnik
Show affiliationsPiezoelectric fluorides of the composition BaMF4 (M = Mg, Zn, Mn) have been studied in situ at high pressures in diamond anvil cells with single-crystal x-ray diffraction and Raman spectroscopy. All three compounds crystallize in the acentric space group Cmc 21 at ambient pressure. BaMgF4 undergoes a reversible second order phase transition to the paraelectric phase (space group Cmcm) at pressures between 5 and 6 GPa. BaZnF4 undergoes a reversible first order phase transition to a monoclinic phase (space group P 11n). Both high- and low-pressure polymorphs coexist in the pressure range 5–7 GPa. BaMnF4 maintains the Cmc 21 structure up to pressures of 4 GPa. Above this pressure the diffraction signal decreases rapidly and at 6 GPa no diffraction signal could be detected in our experiment. The compound does not recover its crystallinity on decompression. A comparison of the effects of external and chemical pressure is presented.
61.50.Ks Crystallographic aspects of phase transformations; pressure effects
61.50.Ah Theory of crystal structure, crystal symmetry; calculations and modeling
64.70.K- Solid–solid transitions
62.50.-p High-pressure effects in solids and liquids
77.84.Bw Elements, oxides, nitrides, borides, carbides, chalcogenides, etc.
Issue 21 (1 June 2011)
Received 20 December 2010, in final form 28 March 2011
Published 9 May 2011
J M Posse et al 2011 J. Phys.: Condens. Matter 23 215401
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