## 5 HTS Tapes Studies Using Scanning Electron Microscope
### Analysis of the Chemical Composition of the SF12100-CF Tape (2 \(\mu\)m Ag)--the Control Sample  
Figure 15 shows the SEM images of a cross-section of the SF12100-CF tape (2 \(\mu\)m Ag)--the control sample--with the area marked for which the analysis was performed (pink rectangle), and the obtained EDS spectra and chemical composition.  
The chemical composition analysis in the area--Spectrum 1--with a thickness of about 2 \(\mu\)m, mainly with the presence of silver and small amounts of oxygen (2.46%), is recorded. In the area--Spectrum 2--there are significant amounts of silver (65.75%), but, at the same time, the presence of copper (18.49%) and oxygen (9.43%), as well as small amounts of germanium and yttrium, are found. The measurement was performed at a level of about 2-2.5 \(\mu\)m, i.e., in the area of the silver-YBCO boundary (which is difficult to identify in the photo), which may be the reason for the occurrence of elements in both layers. In the next area--Spectrum 3--there are only elements originating from the superconductor. In the remaining examined areas (Spectrum 4 and Spectrum 5), there are mainly elements characteristic of buffer layers.  
Figure 15: _Cont._Chemical Composition Analysis of the SF12100-CF Tape (2 \(\mu\)m Ag)--the Sample with Reduced Critical Current Value  
Figure 16 shows the SEM images of a cross-section of the SF12100-CF tape (2 \(\mu\)m Ag)--a sample with a reduced I\({}_{\text{C}}\) value--with the area for which the analysis was performed marked (pink rectangle), and the obtained EDS spectra and chemical composition.  
Figure 16: Cont.  
Figure 15: SEM images of the cross-section of the HTS tape (2 \(\mu\)m Ag)—the control sample—and the EDS spectra and elemental composition evaluations: (a) the area corresponding to the silver layer, (b,c) the superconductor layer, and (d,e) the buffer layers.  
Figure 16: SEM images of the HTS tape cross-section (2 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 elements from the silver and superconductor layers, (**c**) the superconductor layer, and (**d**,**e**) the buffer layers.  
The analysis of the elemental composition in the first area (Spectrum 6) showed only silver (Figure 16a). Then, at the level of about 2-2.5 \(\upmu\)m (Spectrum 7), similarly to the control sample, silver, copper, germanium, and yttrium were present, but the silver content dropped from 65.75% to 25.53%, while the amount of oxygen (from 9.43% to 22.67%) and copper (from 18.49% to 38.53%) increased significantly. The content of other elements characteristic of the superconductor also increased. Similar to the tape with a 4 \(\upmu\)m thick silver layer with a reduced I\({}_{\rm C}\) value, this may indicate the occurrence of diffusion between the silver and YBCO. In this area, there were also bright areas that may indicate silver oxidation. In the area--Spectrum 8--only elements originating from the superconductor occur. In the lowest areas (Spectrum 9 and Spectrum 10), there are elements characteristic of the buffer layers, but also elements from the YBCO layer.  
In the tested samples (the control sample and the samples subjected to the expected short-circuit currents), no significant changes in the amount of copper and oxygen for the YBCO layer are observed. It is difficult to provide an unambiguous interpretation of the individual results obtained. More complete information could be obtained based on the study of a large number of samples and statistical analyses of the obtained results.