Synthesis and First-Principles Studies of Single-Crystalline β-BC₂N with Oxygen-Bearing Defects

Abstract

Single-crystalline B-C-N nanorods were prepared at 500 °C and less than about 20 MPa. Results from X-ray powder diffraction (XRD) and selected-area electron diffraction (SAED) measurements suggest that the synthesized single-crystalline B-C-N is of tetragonal structure and its lattice constants are a ) 7.12(5) Å and c ) 3.57(3) Å. The nanorods all are very straight, and the ratios of length to diameter are between 5 and 30. High resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) observations confirm the well-defined nanorods grown preferentially perpendicular to the [220] direction develop tetragonal morphologies. The energy-loss spectroscopy (EELS) and energy-dispersive X-ray (EDX) elemental mapping confirm that the nanorod is composed of B, C, N, and a trace of oxygen, and its stoichiometry is determined to be close to BC 2 N. First-principles calculations confirm that the as-prepared sample is superlattice phase of β-BC 2 N phase with defects of the C N ′ and the O N ′. In addition, it is a semiconductor material with a direct energy band gap 1.21 eV. The calculated hardness is comparable to that of diamond.

Surperhard monoclinic BC6N allotropes: First-principles investigations*

“…Zhao et al [5] successfully synthesized stoichiometric c-BC 2 N and c-BC 4 N crystals with diamondlike structures by using a diamond-anvil cell. Then Fan et al [6][7][8][9][10][11][12][13][14][15] did systematic investigations of these structures based on the first-principles calculations, such as crystal structure, band gap, optical spectrum, ideal strength and hardness, in order to establish facts and reach new conclusions.…”

Synthesis and Characterization of New “BCN” Diamond under High Pressure and High Temperature Conditions

“…[19][20][21][22][23][24][25] Previous studies have reported the synthesis of cubic B-C-N compounds under HPHT conditions. [26][27][28][29][30] A cubic B-C-N phase has been successfully synthesized by Badzian at 14 GPa and 3300 K starting from the graphitic B-C-N, 26 and Kakudate et al 31 have claimed the formation of a cubic B-C-N substance by a shock-wave technique. Knittle et al have also reported the presence of cubic B-C-N both in the microcrystalline B-C-N compounds and the graphite-structured mixture of BN and C as starting materials, prepared at 30 GPa and 1500 K. Moreover, a mixture of diamond, c-BN, and cubic B-C-N substances is produced by Nakano et al under 7.7 GPa in the temperature range from 2420 to 2570 K, but the cubic B-C-N substance tends to decompose into diamond and c-BN at higher temperatures, which suggests that the cubic B-C-N compound is not thermodynamically stable.…”

“…Considering that the carbon and boron nitride have the same types of polymorphs, such as hexagonal forms (graphite and h-BN) and cubic ones (diamond and c-BN), a cubic B−C−N alloy would be expected to be prepared by transformation from HPHT conditions, by analogy with the preparation of diamond and c-BN from their hexagonal polymorphs. − Previous studies have reported the synthesis of cubic B−C−N compounds under HPHT conditions. − A cubic B−C−N phase has been successfully synthesized by Badzian at 14 GPa and 3300 K starting from the graphitic B−C−N, and Kakudate et al have claimed the formation of a cubic B−C−N substance by a shock-wave technique. Knittle et al have also reported the presence of cubic B−C−N both in the microcrystalline B−C−N compounds and the graphite-structured mixture of BN and C as starting materials, prepared at 30 GPa and 1500 K .…”