The influence of Ag substitution on structural and mechanical properties of (Bi, Pb)-2223 ceramics

In this work, Bi_1.7Pb_0.3Sr₂Ca₂Cu_3−xAg_xO_y (x = 0.00, 0.03, 0.06, 0.09, 0.12) ceramics were prepared by conventional solid state reaction method. The effects of Ag substitution on the structural and mechanical properties of the samples were investigated by Vickers microhardness, X-ray powder diffraction (XRD) measurements and scanning electron microscope (SEM) analysis. The phase formation, volume fraction and lattice parameters were characterized by using XRD measurements. Surface morphology and grain connectivity of the samples were identified by using SEM. The mechanical properties were analyzed by microhardness measurements. Load dependent microhardness, elastic modulus, yield strength and fracture toughness were obtained by hardness measurements. XRD results indicated that the lattice parameter c decreases with increasing Ag addition. It was also observed that volume fraction of Bi-2223 phase decreases with increasing Ag addition from XRD measurements. SEM results showed that the surface morphology and grain connectivity improve, the grain sizes and porosity of the samples decrease with increasing Ag addition. Vickers microhardness (H_v), Young’s modulus (E), yield strength (Y) and fracture toughness (K_IC) values were calculated separately for all samples. In our study, Young’s modulus, yield strength, and fracture toughness of the samples indicated dependency on applied load. It was seen that the load dependent H_v, E, Y, and K_IC increase with increasing Ag and decreasing applied load. Experimental results of the microhardness measurements were analyzed using two models such as elastic–plastic deformation model and the energy dissipative model. Energy dissipative model was determined as the most successful model describing the mechanical properties of our samples.