## 3 Results and Discussion
### Thermal Stability under In Situ TEM Heating  
Figure 4 shows BF TEM images and SAED patterns of Ta-Zr-Si-B-C coatings obtained during in situ TEM heating. According to the BF images, heating at temperatures of 200-800 \({}^{\circ}\)C led to insignificant changes in the structure, while at a temperature of 1000 \({}^{\circ}\)C, after holding for 10 min, the coating crystallized (Figure 4a). It can be seen from the SAED patterns that the amorphous structure of the Ta-Zr-Si-B-C coating is retained up to a temperature of 400 \({}^{\circ}\)C (Figure 4b). At 600 \({}^{\circ}\)C, reflections from the (111) and (211) h-TaSi\({}_{2}\) crystalline phases with d/n = 0.229 and 0.153 nm are observed on the SAED patterns. A reflection with d/n = 0.132 nm was  
Figure 3: XPS spectra of Ta4f (**a**), Zr3d (**b**), N1s (**c**) and Si2p (**d**) for Ta-Zr-Si-B-N as-deposited coatings after etching for 5 min. also observed, provided by the cubic phase of c-TaC (311) (JCPDS 65-8145). Raising the temperature to 1000 \({}^{\circ}\)C led to a narrowing of the reflections and the formation of a more pronounced crystal structure. For a more detailed study of the change in the structure of the Ta-Zr-Si-B-C coating during heating, the FWHM parameter was determined (Figure 5). It can be seen that the FWHM parameter for the carbon-containing coating somewhat decreased in the range of 20-800 \({}^{\circ}\)C, which is associated with the narrowing of reflections as a result of structure ordering (Figure 4b). A pronounced decrease in temperature within 800-1000 \({}^{\circ}\)C indicates an accelerated crystallization of the coatings. The crystallite sizes corresponding to the FWHM parameter at temperatures of 800 and 1000 \({}^{\circ}\)C were \(\sim\)3 and \(\sim\)18 nm, respectively. Figure 6 shows BF TEM images and SAED patterns of the Ta-Zr-Si-B-N coating obtained in the temperature range 600-1000 \({}^{\circ}\)C.  
Figure 4: BF TEM images at temperatures of 200–1000 \({}^{\circ}\)C (**a**) and SAED patterns (**b**) at temperatures of 600–1000 \({}^{\circ}\)C for the Ta-Zr-Si-B-C coating. Figure 5: FWHM parameter for Ta-Zr-Si-B-C and Ta-Zr-Si-B-N coatings depending on temperature. The results showed that heating in this temperature range did not lead to a change in the structural-phase state of the Ta-Zr-Si-B-N coating (Figure 6a). In all cases, the SAED patterns exhibited broad reflections (Figure 6b) typical of amorphous materials [45]. Crystallization of the coating was observed only during exposure at a temperature of 1000 \({}^{\circ}\)C. Shooting BF TEM images at low magnification made it possible to register the movement of the crystallization front at a speed of 10 nm/s (Figure 7). A video of the crystallization process is given in the Supplementary Material (Video S1). Figure 8 shows the EDS data of Ta-Zr-Si-B-N coating lamellas after in situ TEM heating at 1000 \({}^{\circ}\)C.  
Figure 6: BF TEM images (**a**) and SAED patterns (**b**) at temperatures of 600, 800 and 1000 \({}^{\circ}\)C, recorded during exposure (**b**), for the Ta-Zr-Si-B-N coating. Figure 7: BF TEM images obtained for the Ta-Zr-Si-B-N coating at 1000 \({}^{\circ}\)C at various exposition times (Supplementary Material, Video S1). At a maximum exposure of 10 min, the formation of local areas of grain accumulation (dark areas in TEM images) rich in platinum was observed (Figure 8, points 1, 2). According to EDS analysis, the studied zone at the lamella boundary (point 3) corresponded to the coating material and had the following composition: 76 wt.% Ta, 10.7 wt.% Si, 9.9 wt.% Zr and 4.4 wt.% N. Note that the determination of the boron concentration using the EDS method is difficult. The process of crystallization and grain growth is well described by the SAED patterns taken during holding at 1000 \({}^{\circ}\)C (Figure 6b). It can be seen that at the initial moment of time (0-5 min), small crystallites are formed, giving reflections in the form of rings, the order of which corresponds to the FCC structure.