Microhardness measurements on dopant modified superconducting YBa2Cu3O7 ceramics

Abstract

We have studied the microhardness of undoped and dopant modified YBa2Cu3O7 superconducting ceramics as a function of load and dopant concentration using the Vickers indentation technique. In the undoped composition, the hardness value increased monotonically with decreasing load. We concluded that the higher hardness values, measured at lower loads, represent the hardness of single-crystalline grains. The higher loads [∼100–200 gf (1–2 N)] usually resulted in complex crack patterns and extensive crack propagation along the grain boundaries. With Zn or Li as the substitutional dopant in the Cu site, the hardness increased linearly with the dopant concentration up to 10% of dopant to Cu ratio at a load of 25 gf (0.25 N). Our data can be modeled by a solute solution strengthening mechanism.