Abstract
This study focuses on the phase changes occurring in superconducting thick films of Bi2Sr2Ca1Cu2Ox printed from a novel nitrate paste on single-crystal MgO. By optimizing the firing profile, the ratio of the 2.4 nm to 3.0 nm phase could be controlled to achieve reproducibleTo values of 85 K. A model for the 2.4 nm to 3.0 nm phase transformation is proposed, based on SEM and X-ray diffraction data. Two unit cells of the 2.4 nm phase may transform to one 3.0 nm phase unit cell by losing two bismuth oxide layers and one strontium oxide layer. Sr, Bi-rich particles were observed by SEM after the transformation. The degradation of the thick films with ageing at room temperature may be related to possible SrCO3 and/or CaCO3 formation.
Published Version
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