## 3 Results and Discussion
### Thermal Stability under Vacuum Annealing  
XRD patterns of coatings annealed in vacuum according to modes similar to TEM are shown in Figure 9.  
Figure 9: XRD patterns of Ta-Zr-Si-B-C (**a**) and Ta-Zr-Si-B-N (**b**) coatings after vacuum annealing at temperatures of 600, 800 and 1000 \({}^{\circ}\)C.  
For the Ta-Zr-Si-B-C coating (Figure 9b), an increase in temperature from 20 to 600 and 800 led to the separation of peaks in the 20 = 20-50 and 55-75 and an increase in their intensity, which indicates phase segregation. At a temperature of 1000, crisp peaks corresponding to reflections from the (100), (101), (102), (111), (112) and (114) planes of the h-TaSi\({}_{2}\) phase and the (111), (200) and (220) planes of the c-TaC phase were detected on the XRD patterns. The size of the h-TaSi\({}_{2}\) and c-TaC crystallites, determined by the most intense lines (111) using the Scherrer formula, was \(\sim\)20 and \(\sim\)10 nm, respectively. According to XRD patterns, the amorphous structure of the Ta-Zr-Si-B-N coating was retained up to a temperature of 800. At 1000, crystallization of the Ta-Zr-Si-B-N coating was observed with the formation of h-TaSi\({}_{3}\) and c-TaN phases. In this case, the size of h-Ta\({}_{5}\)Si\({}_{3}\) and c-TaN crystallites, determined from the (211) and (111) lines, was \(\sim\)10 and \(\sim\)6 nm, respectively. In addition, the increase in the XRD intensity with the annealing temperature indicates that the number of crystallites increases and the coating becomes more crystalline [48]. The XPS spectra of Ta4f, Si2p and C1s for the Ta-Zr-Si-B-C coating after vacuum annealing at temperatures of 600, 800 and 1000 are shown in Figure 9. The positions of the Ta-Si and Ta-C lines in the Ta4f spectra (Figure 10a) remained almost unchanged from a temperature rise from 20 to 1000. The increase in the intensity of the Ta-C peaks is associated with an increase in the volume fraction of this bond in the coating. The XPS spectra of Si2p (Figure 10b) of the Ta-Zr-Si-B-C coating show that an increase in temperature from 20 to 800. does not lead to changes: Si-C and Si-Si bonds are observed in the coating in positions similar to the as-deposited coating. Heating to 1000 led to a change in the Si2p spectrum: a broad peak was observed at position 101.4 eV, corresponding to the Si-C bond. It can be assumed that with an increase in temperature from 800 to 1000, all free silicon went to the formation of Si-C bonds, which is also evidenced by an increase in the intensity of the Si-C peak at an energy of 283.4 eV in the spectrum of C1s (Figure 10c). The XPS spectra of Ta4f, Si2p and N1s for the Ta-Zr-Si-B-N coating after vacuum annealing are shown in Figure 11.  
Figure 10: XPS spectra of Ta4f (**a**), Si2p (**b**) and C1s (**c**) for Ta-Zr-Si-B-C coatings after vacuum annealing at temperatures of 600, 800 and 1000. According to the Ta4f spectra (Figure 11a), the Ta-Zr-Si-B-N coating is heated from 20 to Si towards a lower binding energy, which is associated with an increase in the fraction of tantalum in Ta-Si bonds [49] and indicates the formation of the Ta\({}_{5}\)Si\({}_{3}\) phase. The Si2p spectra (Figure 11b) show that an increase from 20 to 800 \({}^{\circ}\)C is accompanied by a decrease in the intensity of the Ta-Si peak. At 1000 \({}^{\circ}\)C, the division of the peak (97-100 eV) into two peaks at the positions 98.4 eV and 99.0 may be due to an increase in the fraction of tantalum in Ta-Si and the release of free silicon (Si-Si bond) due to the h-TaSi\({}_{2}\) phase transition to h-Ta\({}_{5}\)Si\({}_{3}\). At the same time, the intensity of the Si-N peak decreased. This effect is associated with the redistribution of silicon atoms between Si-N and Ta-Si with increasing temperature. The appearance of the N1s (Figure 11c) spectra practically did not change with increasing temperature. It is important to note that the in situ TEM, FWHM, XRD and XPS data correlate well with each other.