Click here to view fulltext PDF

Permanent link:
https://www.ias.ac.in/article/fulltext/pram/036/02/0133-0141

Raman spectroscopy; high pressure; diamond anvil cell; phase transition

The effect of pressure on the Raman modes in TeO₂ (paratellurite) has been investigated to 30GPa, using the diamond cell and argon as pressure medium. The pressure dependence of the Raman modes indicates four pressure-induced phase transitions near 1 GPa, 4.5 GPa, 11 GPa and 22 GPa. Of these the first is the well studied second-order transition fromD₄⁴ symmetry toD₂⁴ symmetry, driven by a soft acoustic shear mode instability. The remarkable similarity in the Raman spectra of phases I to IV suggest that only subtle changes in the structure are involved in these phase transitions. The totally different Raman spectral features of phase V indicate major structural changes at the 22GPa transition. It is suggested that this high pressure-phase is similar to PbCl₂-type, from high pressure crystal chemical considerations. The need for a high pressure X-ray diffraction study on TeO₂ is emphasized, to unravel the structure of the various high pressure phases in the system.

A Jayaraman¹ G A Kourouklis^{1 2}

1. AT&T Bell Laboratories, Murray Hill, New Jersey - 07974, USA
2. Physics Division, School of Technology, Aristotle University of Thessaloniki, Thessaloniki - 54006, Greece

Published

February 1991

Manuscript received

10 August 1990