Phase relations in boron at pressure up to 18 GPa and temperature up to 2200 {\deg}C

TL;DR

This study explores the phase diagram of boron under high pressure and temperature, identifying stable and metastable phases and their boundaries using experimental techniques.

Contribution

It provides new experimental data on boron phase relations up to 18 GPa and 2200°C, including synthesis conditions and phase boundaries.

Findings

γ-B28 can be synthesized over a wide P-T range

T-B50 forms at higher temperatures and similar pressures

Phase boundaries between β-B106, γ-B28, and T-B50 are mapped

Abstract

The phase relations in boron have been investigated at high pressure and high temperature using a multianvil apparatus, and the quenched sample has been analyzed by x-ray diffraction, Raman spectra and transmission electron microscopy. We demonstrate that {\gamma}-B28 can be synthesized over a wide P-T range, and T-B50 is obtained at higher temperatures and similar pressures. The phase boundary of the {\beta}-B106, {\gamma}-B28 and T-B50 is determined at pressures between 7 and 18 GPa and the temperatures of 500-2200 {\deg}C. The results suggest that T-B50 might be an intermediate phase-metastable, formed for kinetic reasons (Ostwald rule) on the way from {\beta}-B106 to T-192 and {\gamma}-B28 to T-192.