High-pressure phase transformations of CuGeO3

Ming, L. C. ; Shieh, S. R. ; Jayaraman, A. ; Sharma, S. K. ; Kim, Y. H. (1999) High-pressure phase transformations of CuGeO3 Journal of Physics and Chemistry of Solids, 60 (1). pp. 69-81. ISSN 0022-3697

Full text not available from this repository.

Official URL: http://www.sciencedirect.com/science/article/pii/S...

Related URL: http://dx.doi.org/10.1016/S0022-3697(98)00244-3


In situ powder X-ray diffraction studies were carried out on CuGeO3 to 42 GPa in a diamond-anvil cell, using synchrotron radiation. The results obtained show that the phase transformation sequence in CuGeO3 is dependent on the pressure-medium employed, in accord with the previous Raman/optical observations. In experiments using 4:1 methanol/ethanol mixture as the pressure medium, the sample exhibits the following sequence of pressure-induced transformation on the compression cycle: orthorhombic phase (I)→orthorhombic phase (II) at ∼7 GPa→monoclinic distorted phase (II′) at ∼20.5 GPa→tetragonal garnet-like phase (VI) at 32 GPa. During the decompression cycle phase (VI) persists down to 18.7 GPa and coexists with a monoclinic phase (VII) down to 5.5 GPa, then to an orthoenstatite-like phase (VIII) at 3 GPa and finally to a different orthorhombic phase (I′) at atmospheric pressure. The recovered phase (I′) is closely related to the original phase (I). In the experiments with NaCl as the pressure medium, the phase transformation sequence is phase (I) to a monoclinic phase (IV) (green phase) at ∼8 GPa, which in turn transforms to an orthorhombic phase (V) at 18.4 GPa. On release of pressure to the ambient, the quenched sample has a deep blue colour [phase (III)], which has orthorhombic symmetry. Volume data obtained on CuGeO3 (I) under hydrostatic pressure would be consistent with a bulk modulus (K0) of 39.5 GPa and K0′ of 8.5 for phase (I), as reported in a very recent measurement under truly hydrostatic conditions. However, P–V data obtained with NaCl as the pressure medium yield a bulk modulus K0=66±2 GPa. These results demonstrate that the deviation from strict hydrostaticity profoundly influences the high pressure behaviour of CuGeO3.

Item Type:Article
Source:Copyright of this article belongs to Elsevier Science.
Keywords:C. High Pressure; A. Oxides; C. X-Ray Diffraction; D. Phase Transition
ID Code:96109
Deposited On:04 Dec 2012 09:55
Last Modified:04 Dec 2012 09:55

Repository Staff Only: item control page