High-pressure x-ray diffraction study on the structure and phase transitions of the defect-stannite ZnGa2Se4 and defect-chalcopyrite CdGa2S4

TL;DR

This study investigates the structural changes and phase transitions of ZnGa2Se4 and CdGa2S4 under high pressure using X-ray diffraction, revealing pressure-induced phase transitions and their relation to cation disorder.

Contribution

It provides detailed high-pressure structural data for ZnGa2Se4 and CdGa2S4 and compares these with other sphalerite-related compounds, highlighting trends in transition pressures.

Findings

ZnGa2Se4 remains stable up to 15.5 GPa with a coexistence phase up to 23 GPa

CdGa2S4 transitions from chalcopyrite to NaCl-type structure above 17 GPa

Transition pressure correlates with cation and anion radii ratios

Abstract

X-ray diffraction measurements on the sphalerite-derivatives ZnGa2Se4 and CdGa2S4 have been performed upon compression up to 23 GPa in a diamond-anvil cell. ZnGa2Se4 exhibits a defect tetragonal stannite-type structure (I-42m) up to 15.5 GPa and in the range from 15.5 GPa to 18.5 GPa the low-pressure phase coexists with a high-pressure phase, which remains stable up to 23 GPa. In CdGa2S4, we find the defect tetragonal chalcopyrite-type structure (I-4) is stable up to 17 GPa. Beyond this pressure a pressure-induced phase transition takes place. In both materials, the high-pressure phase has been characterized as a defect-cubic NaCl-type structure (Fm-3m). The occurrence of the pressure induced phase transitions is apparently related with an increase of the cation disorder on the semiconductors investigated. In addition, the results allow the evaluation of the axial compressibility and the determination of the equation of state for each compound. The obtained results are compared with those previously reported for isomorphic digallium sellenides. Finally, a systematic study of the pressure-induced phase transition in twenty-three different sphalerite-related ABX2 and AB2X4 compounds indicates that the transition pressure increases as the ratio of the cationic radii and anionic radii of the compounds increases.