Microhardness anisotropy of Bi-2212 crystals

• Published in: Physica. C, Superconductivity Superconductivity, 1998-09, Vol.306 (3), p.213-217
• Main Authors: Ionescu, M., Zeimetz, B., Dou, S.X.
• Format: Article
• Language: English
• Subjects: Anisotropy; Bi-2212; Bismuth based superconductors; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; High temperature superconductor; Mechanical and acoustical properties, elasticity, and ultrasonic attenuation; Microhardness; Physics; Properties of type I and type II superconductors; Superconductivity
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/S0921-4534(98)00394-3

The microhardness of a high quality Bi-2212 crystal, grown by using the temperature gradient method, was measured with the direction of the applied force parallel, and perpendicular to the ( a, b) crystallographic plane. The measurement was carried out using a technique which is capable to monitor both the applied force, and the displacement of the indenter relative to the sample surface. A maximum force of 10 mN was used, applied in 20 steps in a square root sequence on a diamond pyramid indenter, having a tip radius of 1 μm. From the load–unload cycle, a number of physical parameters of the Bi-2212 phase were deduced: Young's modulus, Poisson's ratio, the yield strength in compression, the elastic recovery rate, and the energy loss during the indentation process. The results show a strong hardness anisotropy between the two directions of the applied force: 3.78 GPa for the applied force perpendicular, and 0.78 GPa for the applied force parallel to the ( a, b) crystallographic plane.