Discovery of Metastable W₃P Single Crystals with High Hardness and Superconductivity

Abstract

Hard and superconducting materials play significant roles in their respective application areas and are also crucial research fields in condensed matter physics. Materials with the key properties of both hard and superconducting properties could lead to technology development, but it is also full of challenges. Herein, we report the synthesis of high-quality metastable W3P single crystals with superconductivity and excellent mechanical properties. The synergistic effect of temperature and pressure was effective in suppressing further decomposition of metastable W3P as-synthesized by our synthesis technique (high-pressure and high-temperature method). The transport and magnetic measurements indicate that W3P is a typical type-II BCS superconductor, displaying a superconducting transition temperature of 5.9 K and an impressive critical magnetic field of 4.35 T. Theory calculations reveal a metallic property in W3P, and the phonon modes of the vibration of W atoms are important for electron–phonon interaction. Meanwhile, W3P shows excellent mechanical properties with a high fracture toughness of 8 MPa m1/2 and an impressive asymptotic hardness of 22 GPa, which is currently reported as being the hardest among transition metal phosphides. It opens up a new class of advanced materials that combine excellent mechanical properties with superconductivity.

Amorphous diamond embedded in dense boron nitride with excellent mechanical properties

“…The Vickers hardness of the recovered samples at 25 GPa and the temperature from 1,000 to 1,800 °C are estimated using a hardness tester with a load of 9.8 N. As shown in Figure 1B and C, the Vickers hardness of the samples increases gradually from 1,000 to 1,400 °C. As shown in Supplementary Figure 3, the recovered samples at 1,400 °C achieve an asymptotic hardness of around 86.2 GPa at approximate 8 N load [Supplementary Figure 4], harder than polycrystalline w-BN and polycrystalline c-BN [30,39] . The increase in hardness is attributed to the transformation of non-dense boron nitride (h-BN and compressed h-BN) into dense-phase boron nitride.…”

“…The amorphous/crystalline strategy may provide a promising way to achieve the high strength of materials that can resist deformation and improve mechanical performance. Despite the extensive successes of preparations of crystalline diamond/c-BN composites, there is no exploration about amorphous-crystalline compounds of amorphous diamond-like carbon and boron nitride [27][28][29][30] .…”