| Summary: | In this paper influence of the excess Ca and Cu cations on the critical temperature (Tc) and critical transport current density (J<sub>c</sub>) of high-temperature superconducting ceramics of the compositions (HTSC) Bi<sub>1</sub><sub>.</sub><sub>6</sub>Pb<sub>0</sub><sub>.</sub><sub>4</sub>Sr<sub>2</sub>Ca<sub>2</sub><sub>.</sub><sub>1</sub>Cu<sub>3</sub><sub>.</sub><sub>1</sub>O<sub>y</sub>, Bi<sub>1</sub><sub>.</sub><sub>6</sub>Pb<sub>0</sub><sub>.</sub><sub>4</sub>Sr<sub>2</sub>Ca<sub>2</sub><sub>.</sub><sub>25</sub>Cu<sub>3</sub><sub>.</sub><sub>25</sub>O<sub>y</sub> and Bi<sub>1</sub><sub>.</sub><sub>6</sub>Pb<sub>0</sub><sub>.</sub><sub>4</sub>Sr<sub>2</sub>Ca<sub>3</sub>Cu<sub>4</sub>O<sub>y</sub> synthesized by the glass-ceramic method has been studied. The synthesis of superconducting ceramics was carried out on the basis of the glass phase, obtained by ultra-fast quenching of the melt. Melting of the mixture of starting components was carried out without the use of a crucible under the influence of IR radiant heating. Analysis of the elemental composition of the samples of the initial precursors showed a significant deviation from stoichiometry in oxygen (increase), as well as a decrease in calcium content. The synthesis of HTSC ceramics was carried out at a temperature of 849–850 °C for 96 h with intermediate grinding every 24 h. Studies of the phase composition of ceramic samples by X-ray diffraction have shown that HTSC ceramics consist only of a superconducting high-temperature phase Bi-2223. Studies of current-carrying characteristics by the four-point probe method according to the criterion of 1 µV/cm<sup>2</sup> have shown that high-temperature superconducting ceramics of the compositions Bi<sub>1</sub><sub>.</sub><sub>6</sub>Pb<sub>0</sub><sub>.</sub><sub>4</sub>Sr<sub>2</sub>Ca<sub>2</sub><sub>.</sub><sub>1</sub>Cu<sub>3</sub><sub>.</sub><sub>1</sub>O<sub>y</sub>, Bi<sub>1</sub><sub>.</sub><sub>6</sub>Pb<sub>0</sub><sub>.</sub><sub>4</sub>Sr<sub>2</sub>Ca<sub>2</sub><sub>.</sub><sub>25</sub>Cu<sub>3</sub><sub>.</sub><sub>25</sub>O<sub>y</sub> and Bi<sub>1</sub><sub>.</sub><sub>6</sub>Pb<sub>0</sub><sub>.</sub><sub>4</sub>Sr<sub>2</sub>Ca<sub>3</sub>Cu<sub>4</sub>O<sub>y</sub> have an increased density of critical transport current of 9.12 A/cm<sup>2</sup>, 7.62 A/cm<sup>2</sup> and 7.26 A/cm<sup>2</sup>, respectively. At the same time, it was found that with a decrease in the content of Ca and Cu cations in HTSC ceramics, an increase in the critical current density is observed.
|
|---|