## 3 Results
### Middle Infrared Spectroscopy (MIR) Measurements
The next two bands 991 and 1088 cm\({}^{-1}\) for glaze 1 correspond to asymmetric stretching vibrations containing Si-O(Al) and Si-O(Si) bridges, respectively. A shift of these bands toward lower wavenumbers can be observed with the increase of potassium oxide in the glaze composition. For the bands corresponding to the silica bridges, an increase in the integral intensity is also observed with an increase in potassium oxide in the glaze composition. For glazes 1, 2, and 3, the presence of the bands 1028, 1039, and 1041 cm\({}^{-1}\) was found, which is related to the presence of andesine and corresponds to the asymmetric stretching vibrations of the aluminum and silica bridges in this crystalline phase. For glazes 4 and 5, the presence of this band is not observed, which is related to the presence of andesine in not a very large amount (9.4 vol.%) and the absence of glaze 5 (Table 4). In the group of asymmetric stretching vibrations (1157-1171 cm\({}^{-1}\)), there are also bands related to the Si-O stretching vibrations, which correspond to silica tetrahedrons connected by edges. The increase in the amount of potassium oxide in the glaze caused a shift of these bands toward higher wavenumbers and a slight increase in their integral intensity, suggesting a quantitative increase in these defects and, thus, a greater disorder in the glaze structure. These results may suggest that with the increase in the amount of potassium oxide in the glaze composition, there is a modification of the internal structure caused by a change in the phase composition and a change in the chemical composition of the amorphous phase. The presence of the crystalline phase of andesine, which belongs to the plagioclase group, in this case, sodium feldspar with calcium cation substitutions in the structure, can itself be significantly damaged. With an increase in the amount of potassium oxide, the observed decrease in the amount of this crystalline phase causes the integral intensity of the bands corresponding to the broken aluminum and silica bridges to decrease. The band responsible for asymmetric Al-O- stretching vibrations is shifted toward higher wave numbers, while the band responsible for asymmetric Si-O- stretching vibrations does not change its position. The observed increase in the integral intensity of asymmetric vibrations of the bands corresponding to the vibrations of the Si-O (Si) and Si-O (Al) bridge oxides, and the shift of the position of these bands along with the shift of the position of these bands toward a lower wavenumber, suggest that the internal structure of the glazes with \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Glaze 1** & **Glaze 2** & **Glaze 3** & **Glaze 4** & **Glaze 5** &
\begin{tabular}{c} **Band** \\ **Ascription** \\ \end{tabular} \\ \hline
434 (5.8) & 433 (8.0) & 433 (6.0) & 433 (0.9) & 432 (0.6) & \(\varsigma\) (O-Zr-O) \\
467 (5.0) & 465 (6.0) & 462 (8.6) & 451 (29.6) & 454 (26.1) & \(\varsigma\) (O-Si-O) \\  & & & & 524 (0.4) & \(\
u\) (Zr-O-Zr) \\ \hline
541 (4.4) & 541 (3.6) & 542 (2.8) & 541 (0.3) & 540 (0.3) & \\
576 (8.3) & 574 (8.0) & 574 (4.8) & 572 (0.4) & 583 (0.5) & Ring \\
618 (8.7) & 618 (10.7) & 616 (9.8) & 613 (3.9) & 613 (2.4) & structure \\
680 (0.3) & 675 (0.3) & 677 (0.2) & 682 (1.7) & 689 (1.8) & \\ \hline
736 (3.5) & 732 (3.2) & 730 (3.2) & 731 (3.7) & 737 (3.9) & \(\
u\) (Si-O-Al) \\
777 (1.2) & 772 (1.2) & 772 (1.1) & 778 (0.9) & 786 (1.1) & \(\
u\) (Si-O-Si) \\
844 (5.8) & 844 (7.3) & 846 (3.7) & 874 (6.3) & 868 (3.4) & \(\
u\) Al-O-[NB] \\
909 (33.9) & 908 (40.9) & 906 (42.1) & 911 (30.4) & 902 (13.3) & \(\
u\) Si-O-[NB] \\
991 (35.6) & 991 (41.1) & 991 (43.9) & 994 (42.9) & 976 (47.7) & \(\
u\) Si-O-Al \\
1028 (4.8) & 1039 (6.9) & 1041 (7.1) & & & \(\
u\) Si-O-Al,Si \\
1088 (32.9) & 1087 (38.4) & 1086 (38.0) & 1073 (39.0) & 1065 (41.5) & \(\
u\) Si-O-Si \\
1162 (28.1) & 1159 (35.6) & 1157 (32.9) & 1170 (33.0) & 1171 (36.1) & \(\
u\) Si=O \\ \hline \hline \end{tabular}
\end{table}