The Effect of Boron on Equilibrium of Superconducting Phases in Bi-Pb-Sr-Ca-Cu-O System

The crystal structures of type 1234 and 2234 are not found in compositions Bi1-xBxSr2Ca3Cu4Oy and Bi2-xBxSr2Ca3Cu4Oy after synthesis under conditions of ambient pressure P = 1 bar and T = 835 degrees C for tau = 240 h. This conclusion is obtained as a result of the fact that the series of bismuth superconductors Bi1-xBxSr2Ca3Cu4Oy, Bi2-xBxSr2Ca3Cu4Oy, Bi2-xBxSr2Ca2Cu3Oy, Bi1.7-xBxPb0.3Sr2Ca2Cu3Oy with different boron content x = 0-2 were synthesized followed by slow (rate < 10 degrees C/sec) cooling or quenching (< 100 degrees C/sec). Samples of Bi1.7-xBxPb0.3Sr2Ca2Cu3Oy with a boron content of x = 0.5 have a significant (> 35%) proportion of the superconducting phase 2223, regardless of the accuracy of observing the temperature modes of synthesis (in temperature ranges < +/- 10 degrees C) and cooling after it. A model of the effect of boron on phase equilibrium in Bi-Pb-Sr-Ca-Cu-O system is proposed using the process of boron-bismuth glass formation. Therefore, the boron addition during the synthesis of bismuth superconductors will increase the production process reproducibility of phase 2223. Also, this technology can be used at the synthesis of superconductors from the boron-bismuth not very enriched ores in conditions of limited available resources.