Influence mechanism of secondary gel technique on Bi-2212 superconducting phase: Gel model simulation and verification

Abstract

Study of gel structures as precursors for Bi2Sr2Ca1Cu2Ox (Bi-2212) superconductors can provide better understanding of the role of gel process in the synthesis of superconducting phase. However, it is still challenging to investigate the amorphous gel system through conventional methods. Here, based on our former experiments, we present a computer simulation method to establish the geometric structural models of ethylenediaminetetraacetic acid (EDTA)-metal cation complexes, conventional gel and home-made secondary gel. Local orbital density functional method, Dmol3 approach was applied to optimize the structures and compare the thermodynamical stabilities of different systems. In addition, Bi-2212 samples with different sintering time were prepared via both conventional and secondary gel technique to verify the calculation results. Results demonstrated that the secondary gel system possesses higher phase stability compared to the conventional gel owing to its higher bonding ability of EDTA-metal cation complexes. Hence, component homogeneity of complexes can be enhanced and pure Bi-2212 phase can be synthesized with shorter sintering time.