Enhancing Phase Purity of CSD Bi-2223 Thin Films Through Protected Sintering Method

Abstract

Pure Bi 2 Sr 2 Ca 2 Cu 3 O x (Bi-2223) phase is hard to be achieved in Bi-2223 thin films fabricated by using chemical solution deposition (CSD) due to the volatilization of specific elements. Two protected sintering methods were proposed in this work to enhance the phase purity of CSD Bi-2223 thin films. One method is two deposited thin films stacked "face-to-face" (FTF) and then sintered. A "substrate/precursor film/precursor film/substrate" architecture was used during sintering instead of common "precursor film/substrate" architecture. The other method was named "sealed face-to-face" (SFTF). The FTF structure was buried in Bi-2223 powders and then sealed in a silver envelope before sintering. Different sintering temperature and sintering time were investigated in an 8% O 2 (N 2 balance) atmosphere. The volume fraction of Bi-2223 phase could be enhanced to 17% by using the FTF method, and 68% by using the SFTF method.

Biaxially textured (Bi, Pb)2Sr2Ca2Cu3O x thin films on LaAlO3 substrates fabricated via the chemical solution deposition method

“…This study demonstrated the feasibility of (Bi, Pb)-2223 thin films with a considerable J c property being obtained via CSD. Compared to our previous study [28] in which J c was zero, the reason for the improvement in this study can mainly be attributed to the favorable biaxial texture caused by the epitaxial growth, as shown in figures 7 and 8. The a-axial lattice of the LAO substrate (a LAO ) is 0.3789 nm (PDF#850848), while the a-axial and b-axial lattices of (Bi, Pb)-2223 (a 2223 and b 2223 ) are 0.5399 nm and 0.5413 nm (PDF#460745), respectively.…”

“…The FTF structure together with 0.7 g powder of Pb 0.33 Bi 1.80 Sr 1.87 Ca 2.00 Cu 3.00 O x were wrapped in 0.1 mm thick silver foil and sealed by using silver paste. Such a PIF process could help to reduce the evaporation of elements during sintering and improve the quality of the (Bi, Pb)-2223 thin films, as reported in our previous publication [28]. The sealed samples were sintered in 8 vol.% O 2 (N 2 balanced) with a heating rate of 200 °C h −1 and a dwelling at various sintering temperatures (T S ) for 10 h.…”

“…To better understand the phase evolution along with T S increasing, the relative volume fraction of the (Bi, Pb)-2223 phase ( f V2223 ), which was defined and utilized in our previous studies on tape samples [35] and film samples [17,28], was calculated by When T S increased from 800 °C to 830 °C, f V2223 varied from zero to about 20%, indicating the domination of the Bi-2212 phase. When T S was above 835 °C, f V2223 increased significantly, with a maximum value of 86.6% at a T S of 840 °C.…”

“…In our previous study [28], (Bi, Pb)-2223 thin films on silver substrates were fabricated via CSD, and a protected sintering method called 'powder-in-foil' (PIF) was proposed to prevent the evaporation of Bi and Pb, thus enhancing the (Bi, Pb)-2223 phase formation. Although a (Bi, Pb)-2223 volume fraction of 68% was achieved, J c was not detected in the samples, which might be attributed to the non-textured property of silver foil substrates.…”