Original paper

High-pressure Raman spectroscopic study of post-aragonite phase transition in witherite (BaCO3)

Lin, Chung-Cherng; Liu, Lin-Gun

European Journal of Mineralogy Volume 9 Number 4 (1997), p. 785 - 792

14 references

published: Jul 23, 1997
manuscript accepted: Feb 5, 1997
manuscript received: Feb 13, 1996

DOI: 10.1127/ejm/9/4/0785

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Abstract

Abstract By employing Raman spectroscopy, the phase transformation of barium carbonate under both quasihydrostatic and non-hydrostatic conditions was investigated in a diamond-anvil cell up to pressures of 310 kbar at room temperature. The aragonite-type BaCO3 (witherite) is found to transform to a new high-pressure polymorph (BaCO3 II), which has a crystal structure symmetry lower than that of witherite, when the pressure is increased to about 80 kbar. Upon releasing pressure, BaCO3 II remains stable down to 20 kbar and then starts to transform back to witherite at still lower pressures. Thus, the transition possesses a large hysteresis in pressure at room temperature. BaCO3 II is both thermodynamically and kinetically unstable at ambient conditions, but can be preserved for several hours to one month after releasing the pressure. The pressure dependence of Raman frequencies of the various modes for both witherite and BaCO3 II were also studied at room temperature. The frequency of all the Raman modes in both phases increases monotonically with increasing pressure

Keywords

witheritepost-aragonite phasehigh pressurephase transitionRaman spectroscopy