Evaluation of load-independent microhardness values in Plateau regions of Vanadium substituted Bi-2212 ceramics

Abstract

This study reveals extensively effect of homovalent V/Bi partial replacement in Bi2.0-xVxSr2.0Ca1.1Cu2.0Oy ceramic matrix (0.00 <= x <= 0.30) on the key mechanical design performance parameters and load-independent Vickers microhardness parameters in plateau limit region by means of experimental microhardness tests and semi-empiric approaching models. It is found that the vanadium substitution level of x = 0.01 is observed to be optimum amount in the Bi-2212 crystal lattice for refinement of fundamental mechanical properties due to the enhancement in stabilization of durable tetragonal phase, surface residual compressive stress and elastic recovery mechanism. Conversely, from the replacement level of x = 0.01 onwards, the lattice strain field and stress concentration sites enhance significantly depending on the increase of microscopic structural problems, interaction problems between adjacent layers and crack-initiating flaws in Bi-2212 ceramic system. Correspondingly, stress-induced phase transformation begins to play predominant role, and excess vanadium substituted ceramic materials are easily broken at relatively smaller test load. Moreover, the models indicate that every ceramic compound shows standard indentation size effect (ISE) feature due to predominant behavior of elastic recovery in crystal structure. Hence, presence of optimum vanadium ions strengthens typical ISE characteristic behavior. Furthermore, among semi-empirical models the indentation-induced cracking (IIC) model exhibits the highest performance to inspect real microhardness values of Bi2.0-xVxSr2.0Ca1.1Cu2.0Oy ceramic compounds in the plateau limit region.