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Updated: May 24, 2026

Negative Additive Manufacturing of Complex Shaped Boron Carbides
Published on: September 18, 2018
Experimental pressure-temperature phase diagram of boron: resolving the long-standing enigma
Gleb Parakhonskiy1, Natalia Dubrovinskaia, Elena Bykova
1Bayerisches Geoinstitut, Universität Bayreuth, D-95440 Bayreuth, Germany.
Abstract:
Boron, discovered as an element in 1808 and produced in pure form in 1909, has still remained the last elemental material, having stable natural isotopes, with the ground state crystal phase to be unknown. It has been a subject of long-standing controversy, if α-B or β-B is the thermodynamically stable phase at ambient pressure and temperature. In the present work this enigma has been resolved based on the α-B-to- β-B phase boundary line which we experimentally established in the pressure interval of ∼4 GPa to 8 GPa and linearly extrapolated down to ambient pressure. In a series of high pressure high temperature experiments we synthesised single crystals of the three boron phases (α-B, β-B, and γ-B) and provided evidence of higher thermodynamic stability of α-B. Our work opens a way for reproducible synthesis of α-boron, an optically transparent direct band gap semiconductor with very high hardness, thermal and chemical stability.
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