Anisotropy of thermal expansion, elasticity, and electrical resistivity in single-crystal trinickel boride, Ni3B

Experimental determinations were made of the thermal expansion, elastic moduli, and electrical resistivities of Ni3B crystals, which are second-phase inclusions in TiB2-Ni ceramics. Thermal expansion was measured along the major axes of the crystals at temperatures from 300-1000 K. The expansions were all basically linear with temperature, except for a slight curvature below 700 K due to anharmonicity of the atomic interaction potential in the 010 plane below 700 K. Ultrasonic wave velocity trials were employed to quantify the elastic moduli, while four-probe dc inputs characterized the resistivities. A high electrical resistivity coincided with the anomalous thermal expansion in the 010 plane. The 001 plane was judged to be the stiffest and the 100 plane the least stiff.