Melting properties by X-ray absorption spectroscopy: common signatures in binary Fe\u2013C, Fe\u2013O, Fe\u2013S and Fe\u2013Si systems

Eglantine Boulard,Innokenty Kantor,Tetsuo Irifune,Silvia Boccato,Francesca Miozzi,Simone Anzellini,Angelika D Rosa,Marion Harmand,Guillaume Morard,Raffaella Torchio,Paraskevas Parisiades,François Guyot,Daniele Antonangeli

doi:10.1038/s41598-020-68244-3

Abstract

X-ray absorption spectroscopy (XAS) is a widely used technique to probe the local environment around specific atomic species. Applied to samples under extreme pressure and temperature conditions, XAS is sensitive to phase transitions, including melting, and allows gathering insights on compositional variations and electronic changes occurring during such transitions. These characteristics can be exploited for studies of prime interest in geophysics and fundamental high-pressure physics. Here, we investigated the melting curve and the eutectic composition of four geophysically relevant iron binary systems: Fe–C, Fe–O, Fe–S and Fe–Si. Our results show that all these systems present the same spectroscopic signatures upon melting, common to those observed for other pure late 3d transition metals. The presented melting criterion seems to be general for late 3d metals bearing systems. Additionally, we demonstrate the suitability of XAS to extract melt compositional information in situ, such as the evolution of the concentration of light elements with increasing temperature. Diagnostics presented in this work can be applied to studies over an even larger pressure range exploiting the upgraded synchrotron machines, and directly transferred to time-resolved extreme condition studies using dynamic compression (ns) or fast laser heating (ms).

Highlights

The coupling of X-ray absorption spectroscopy (XAS) with laser heated-diamond anvil cell (LH-DAC) is a challenging technical development only recently implemented in synchrotron facilities[1,2,3]
Melting detection methods include visual observation of sample surface movements[35], the plateau in the temperature versus laser power plot[36], appearance of liquid diffuse scattering in X-ray diffraction (XRD) measurements or disappearance of the solid peaks[28,37,38,39,40,41,42,43,44], and ex situ textural analysis (FIB coupled with scanning electron microscope (SEM) or microprobe) on recovered quenched samples[28,32,34,40,44]
We report a systematic study on melting curves of iron-rich binary systems performed by X-ray absorption spectroscopy in combination with laser heated diamond anvil cell

Summary

Introduction

The coupling of X-ray absorption spectroscopy (XAS) with laser heated-diamond anvil cell (LH-DAC) is a challenging technical development only recently implemented in synchrotron facilities[1,2,3]. The element selectivity and the local structure sensitivity are two of the distinctive characteristics that make XAS a very informative and multipurpose technique Combined together, they provide the possibility of microscopic investigation of the local atomic environment of a specific element in a compound or an alloy, irrespectively of the solid, liquid or amorphous state. Melting criteria are generalized and used to probe melting curves of Fe–X binary systems, where X = C, O, S and Si. the quality of the collected data allowed us to apply LCA-based methods for data analysis, obtaining a quantitative in situ determination of chemical composition of the temperature-quenched samples under pressure, during the heating runs.

Methods

Results

Discussion

Conclusion