Phase and microstructure evolution in the process of the composite Bi-2212-(Sr, Ca)₃Al₂O₆glass-ceramics formation

Abstract

Devitrification of glass with a cation ratio corresponding to the composition {Bi2.1Sr2CaCu2Ox+0.4Sr1.7Ca1.3Al2O6} was studied. At temperatures below 600 °C, the phases crystallized in the order Bi-2201, Cu2O, CaO, (Sr,Ca)3Bi2O6, while Al ions concentrated in the remaining glass. Above 600 °C, Bi-2212 and (Sr,Ca)3Al2O6 formed simultaneously, so that at 750 °C, the two-phase composite Bi-2212-(Sr,Ca)3Al2O6 was obtained that contained grains of the aluminate phase 0.03-0.3 µm in size. The Al-rich phase surplus increased the stability of the glass and accelerated Bi-2212 phase formation, while development of superconductivity in Bi-2212 was slowed down. It was shown that composite glass-ceramics with bulk superconductivity could be obtained at temperatures above 850 °C.

Microcomposites based on superconducting cuprates

“…14 c). 208 However, in this case the aluminate grains are partially aggregated in the space between lamellae of the superconducting phase.…”

“…204,205,207 Bi2212-based composites with inclusions of compatible Al-containing oxides have been studied in detail. 164,168,169,208 It was found that the BiSr 1.5 Ca 0.5 Al 2 O z phase is nearly completely segregated in the intercrystalline space of the Bi2212 phase, so that the intergranular electric contacts are broken. At the same time, Sr 1.7 Ca 1.3 Al 2 O 6 mainly forms inclusions inside of the Bi2212 crystallites and, hence, the superconducting current can flow throughout the whole volume of the sample (Fig.…”

Formation of Bi-2212-based composites with submicrometre-grained (Sr, Ca)SnO3

“…Different ways of inclusion formation were investigated. For instance, fine precipitates of the secondary phases were created by partial decomposition of the single-phase superconductor [3,6]; MgO was introduced in the form of micro-or nanosize whiskers and grains [5,[7][8][9]; submicron inclusions of complex metal oxides were formed in the Bi-2212 matrix via processing of the homogeneous precursors [10][11][12][13].…”