An insight into microstructure and structure stability of Ni-doped Bi2212 ceramics

A series of Bi2Sr2-xNixCaCu2O8+delta (x = 0.00, 0.10, 0.20 and 0.30) ceramics samples were synthesized by Pechini sol-gel method. In this work, the microstructure and structure stability of Ni-doped Bi2212 system were investigated particularly by X-ray diffraction, electron microscopy and high-pressure Raman spectroscopy. It is confirmed that the main phase of all samples is the typical Bi2212 tetragonal phase with space group I4/mmm. As Ni-doping amount x <= 0.20, the number of Ni atoms entering the Bi2212 lattice increases gradually with increasing x. These Ni atoms preferentially occupy Sr-sites, resulting in a gradual increase in the a and c axis lengths of Bi2212 structure. The formation of containing-Ni Bi2212 lattice is mainly derived from the insertion of sufficient Ni-O two-dimensional (2D) monomers. Contrarily, when x > 0.20, these Ni-O 2D monomers will preferentially form the NiO particle and the chance of Ni atoms entering the Bi2212 lattice is reduced, which leads to a shrinkage of Bi2212 lattice parameters. Besides, under high-pressure (0-20 GPa) condition, Raman spectrum analysis shows that the O-Sr peak significantly shifts to the higher wavenumber and Bi2212 phase could still maintain the tetragonal structure, suggesting that it has a relatively high structure stability.

Automated summary

A series of Ni-doped Bi2212 ceramics samples were synthesized using the Pechini sol-gel method, and their microstructure and structure stability were investigated using various characterization techniques. The results showed that with increasing Ni-doping amount, Ni atoms preferentially occupied Sr-sites, resulting in an increase in the a and c axis lengths of the Bi2212 structure. Additionally, under high-pressure conditions, the Bi2212 phase maintained a relatively high structure stability.