## 5 HTS Tapes Studies Using Scanning Electron Microscope
### Chemical Composition Analysis of the SF12100-CF Tape (4 \(\mu\)m Ag)--the Control Sample  
For the tested sample, the chemical composition of the individual layers of the tape was analyzed. Figure 13 shows the SEM images of the HTS tape cross-section with the area marked for which the analysis was performed (pink rectangle), as well as the obtained EDS spectra and chemical composition--the result was normalized to 100% by mass and atom.  
The top layer of the HTS tape, including the silver, the YBCO superconductor, and buffer layers, was subjected to a detailed evaluation of the chemical composition. Figure 13a-c show the areas of the measurement of the silver layer at three levels due to the large thickness of the Ag layer in this place of the sample and the deformation visible in the photo. Spectrum 16 is located closest to the outer surface of the HTS tape (near the non-conductive resin). Spectrum 17 is located in the middle part of the layer, while Spectrum 18 is located closer to the Ag-YBCO boundary and covers part of the area with the deformation. For Spectrum 18, the presence of copper and oxygen (characteristic of the YBCO layer) was observed, which may indicate that the visible deformation probably occurred at the stage of the HTS tape production. The next areas examined (Spectrum 19) are the YBCO superconductor and the buffer layers (Spectrum 20). The chemical composition of the individual layers is consistent with the manufacturer's description [12].  
Figure 11: Photos of the SF12100-CF tape with a 4 \(\upmu\)m silver layer: (**a**) cross-section photo of the control sample; (**b**) cross-section photo of the sample exposed to the prospective short-circuit currents with marked changes in the YBCO layer.  
Figure 12: Changes in the sample of the HTS tapes SF12100-CF (2 \(\upmu\)m Ag) exposed to prospective short-circuit currents.  
Figure 13: _Cont._  
Analysis of the Chemical Composition of the SF12100-CF Tape (4 \(\mu\)m Ag)--the Sample with Reduced Critical Current Value  
Figure 14 shows the SEM images of a cross-section of the SF12100-CF tape (4 \(\mu\)m Ag) exposed to prospective short-circuit currents and a reduced critical current value, with the area for which the analysis was performed (pink rectangle), and the obtained EDS spectra and chemical composition marked.  
The results of the chemical composition analysis showed changes in the area of the presence of the silver and the superconductor. In the area (Spectrum 11) with a thickness of about 2 \(\mu\)m, the presence of silver and small amounts of oxygen (1.53%) are mainly recorded. The cause of the presence of oxygen may be the oxidation process of the upper silver layer. In the area (Spectrum 12) apart from the silver, there is a significant amount of copper and oxygen, as well as small amounts of yttrium and germanium. The presence of these elements is typical for the superconductor layer, which was lower in the control sample. This may indicate the occurrence of certain diffusion processes between these layers. In the next area (Spectrum 13), only elements originating from the superconductor are present and no presence of silver is observed. In the remaining examined areas (Spectrum 14 and Spectrum 15), there are mainly elements characteristic of buffer layers and the Hastelloy substrate.  
Figure 14: _Cont._  
Figure 13: SEM images of the cross-section of the HTS tape (4 \(\mu\)m Ag)—the control sample—and EDS spectra for the evaluation of the elemental composition: (**a–c**) the area corresponding to the silver layer, (**d**) the superconductor layer, and (**e**) the buffer layers.  
Figure 14: SEM images of the HTS tape cross-section (4 μm Ag) and EDS spectra for the elemental composition assessment—the sample with reduced critical current value: (**a**) the area corresponding to the silver layer, (**b**) the area of the elements from the silver and superconductor layers, (**c**) the superconductor layer, and (**d,e**) the buffer layers.