New high-pressure phase and equation of state of Ce2Zr2O8

TL;DR

This study uncovers a new high-pressure rhombohedral phase of Ce2Zr2O8, detailing its structural transition from cubic, its compressibility, and the pressure dependence of its Raman modes up to nearly 12 GPa.

Contribution

The paper reports the discovery and characterization of a new high-pressure phase of Ce2Zr2O8, including structural details and pressure-dependent properties, expanding understanding of its high-pressure behavior.

Findings

Cubic to rhombohedral phase transition occurs above 5 GPa.

Raman modes show linear pressure evolution in the cubic phase.

Softening of a low-frequency Raman mode observed under pressure.

Abstract

In this paper we report a new high-pressure rhombohedral phase of Ce2Zr2O8 observed from high-pressure angle-dispersive x-ray diffraction and Raman spectroscopy studies up to nearly 12 GPa. The ambient-pressure cubic phase of Ce2Zr2O8 transforms to a rhombohedral structure beyond 5 GPa with a feeble distortion in the lattice. Pressure evolution of unit-cell volume showed a change in compressibility above 5 GPa. The unit-cell parameters of the high-pressure rhombohedral phase at 12.1 GPa are ah = 14.6791(3) {\AA}, ch = 17.9421(5) {\AA}, V = 3348.1(1) {\AA}3. The structure relation between the parent cubic (P2_13) and rhombohedral (P3_2) phases were obtained by group-subgroup relations. All the Raman modes of the cubic phase showed linear evolution with pressure with the hardest one at 197 cm-1. Some Raman modes of the high-pressure phase have a non-linear evolution with pressure and softening of one low-frequency mode with pressure is found. The compressibility, equation of state, and pressure coefficients of Raman modes of Ce2Zr2O8 are also reported.