Syntheses and properties of higher borides from melts in the systems Al-M-B (MÂ =Â Be, Mg, Cu)

Al1.1Be0.7B22, Al1.4Mg0.45B22, AlxCuyB105 (x = 2.8-3.3, y = 2.9-1.0), Al1.3Cu1.1B25 and CuB23 crystals were grown from high-temperature melts of the systems Al-M-B (M = Be, Mg, Cu) and Cu-B in an argon atmosphere. The maximum dimensions of Al1.1Be0.7B22, Al1.4Mg0.45B22, Al3.1Cu2.0B105 and Al1.3Cu1.1B25 crystals were obtained in the ranges of approximately 2.5-5.2 mm. CuB23 crystals prepared had maximum dimensions of approximately 30 μm. The Al1.1Be0.7B22 and Al1.4Mg0.45B22 crystals were obtained as plate-like crystals having well-developed {1 0 1} and {0 0 1} faces, and Al3.1Cu2.0B105 and Al1.3Cu1.1B25 crystals were obtained in the form of needle or rhombohedral plate as bounded by {0 0 1} faces and grew as prismatic shape extending in the c direction. The values of Vickers microhardness on relatively large {1 0 1}, {1 0 0}, {0 0 1} and {0 0 1} faces of Al1.1Be0.7B22, Al1.4Mg0.45B22, AlxCuyB105 (x = 2.8-3.3, y = 2.9-1.0) and Al1.3Cu1.1B25 crystals are in the ranges of 25.4 (0.5) to 27.8 (1.7) GPa. Anomalous magnetic behavior was not observed for any of the compounds, and the good agreement of the temperature independent susceptibility for the AlxCuyB105 compounds with different ratio of metal elements indicate the non-metallic nature of this phase.