Evaluation of the Vickers microhardness and fracture toughness on hot pressed Bi-2212/Ag ceramic composites

Micro-indentation tests provide useful information on mechanical properties such as strength, deformation characteristics and fracture toughness of the ceramic materials. Therefore, a micro-indentation study has been carried out to characterize the mechanical properties of Bi2Sr2Ca1Cu2O8+δ + x wt % Ag (x = 0.0, 0.05, 0.15, 0.25 and 0.50) samples fabricated by hot pressing technique. Vickers hardness, elastic modulus, elastic stiffness coefficient, brittleness index, yield strength, compressive strength, and fracture toughness values of the samples were determined by using apparent micro-hardness. Additionally, load independent values of elastic modulus, elastic stiffness coefficient, brittleness index, yield strength and fracture toughness were also improved by using true microhardness. The experimental results have been analyzed by the theoretical models being proposed in the literature (Meyer’s Law, the elastic/plastic deformation model, proportional sample resistance model, Hays–Kendall model). According to the obtained results, Hays–Kendall model was determined to be as the most suitable model in the plateau region for the all samples showing indentations size effect behavior. The results show that the values of microhardness, strength, elastic parameters and fracture toughness of the samples increased with an increase in the Ag addition. The results exhibit that, it is possible to control the mechanical properties of the Bi-2212 ceramic composites by increasing the Ag addition