## 3 Results and Discussion
### Hydration Behavior
Thus, when oxygen vacancies are completely occupied by the oxygen from H\({}_{2}\)O molecules, the hydration limit can be reached. For the undoped sample La\({}_{2}\)ScZnO\({}_{5.5}\), the observed water uptake was 0.35 mol H\({}_{2}\)O, which is lower than the theoretical value of 0.50 mol H\({}_{2}\)O. That is, the observed water uptake was about 70% of the concentration of oxygen vacancies, which means that not all oxygen vacancies are involved in hydration. This situation is typical for many perovskites. For example, the concentration of protons was measured in oxides based on La\({}_{2}\)O\({}_{3}\): La\({}_{0.9}\)Sr\({}_{0.1}\)MO\({}_{3-8}\) (M = Al, Sc, In, Yb, Y) [53], La\({}_{0.9}\)Sr\({}_{0.1}\) (Yb\({}_{1-x}\)M\({}_{x}\))O\({}_{3-8}\) (M = Y, In) [54], La\({}_{0.9}\)M\({}_{0.1}\)YbO\({}_{3-8}\) (M = Ba, Sr, Ca, Mg) [55], La\({}_{1-x}\)Ba\({}_{x}\)YbO\({}_{3-8}\)[56], La\({}_{1-x}\)Ca\({}_{x}\)ScO\({}_{3-\alpha}\)[33], and La\({}_{1-x}\)Sr\({}_{x}\)ScO\({}_{3-\delta}\)[34]. The authors point out that the concentration of protons does not reach the concentration of oxygen vacancies. Possible reasons are changes in the local structure and the existence of non-equivalent oxygen atoms, trapping oxygen vacancies by acceptor defects. Comparing the obtained TG data for the synthesized phase La\({}_{2}\)ScZnO\({}_{5.5}\) to the data on the hydration of doped scandates LaScO\({}_{3}\), we can conclude that the dehydration of scandates occurs at higher temperatures (T\(\sim\)1000 \({}^{\circ}\)C) and they have significantly lower proton concentrations. All Me\({}^{2+}\)-doped hydrated samples showed approximately the same values of water uptake (\(\sim\)0.48 mol H\({}_{2}\)O for Ca\({}^{2+}\)-doped samples and 0.42 mol H\({}_{2}\)O for Mg\({}^{2+}\)-doped sample) and these values are higher than those for undoped La\({}_{2}\)ScZnO\({}_{5.5}\) (Figure 4). That is, the observed water uptake was about 90% and 75% of the concentration of oxygen vacancies (for Ca\({}^{2+}\) and Mg\({}^{2+}\)-doped samples, accordingly). The doped phases have an additional amount of oxygen vacancies (\(V_{o}^{\bullet\bullet}\)), which appear in accordance with the equations:  
\[2\text{CaO}\overset{La_{2}\text{O}_{3}}{\rightarrow}2\text{Ca}^{\prime}_{\text {La}}+2O_{o}^{\times}+V_{o}^{\bullet\bullet}, \tag{5}\]  
\[2\text{MgO}\overset{Sc_{2}\text{O}_{3}}{\rightarrow}2\text{Mg}^{\prime}_{ \text{Sc}}+2O_{o}^{\times}+V_{o}^{\bullet\bullet}, \tag{6}\]  
\[2\text{CaO}\overset{Sc_{2}\text{O}_{3}}{\rightarrow}2\text{Ca}^{\prime}_{ \text{Sc}}+2O_{o}^{\times}+V_{o}^{\bullet\bullet}. \tag{7}\]  
where \(V_{o}^{\bullet\bullet}\) is the oxygen vacancy, \(O_{o}^{\times}\) is the oxygen atom in a regular position, Ca\({}^{\prime}_{\text{La}}\) is calcium in the lanthanum sublattice, Ca\({}^{\prime}_{\text{Sc}}\) or Mg\({}^{\prime}_{\text{Sc}}\) is calcium or magnesium in the scandium sublattice, respectively. These vacancies interact with water vapor according to the following hydration equation:  
\[V_{o}^{\bullet\bullet}+H_{2}O+O_{o}^{\times}\Leftrightarrow 2(OH)^{\bullet}_{o}, \tag{8}\]where \(V_{o}^{\bullet\bullet}\) is oxygen vacancy, \(O_{o}^{\times}\) is the oxygen atom in a regular position, and \((OH)_{o}^{\bullet}\) is the hydroxyl group in the oxygen sublattice. On the one hand, this can explain an increase in the degree of hydration of doped phases, but a change in the local structure upon the introduction of the dopants can also lead to an increase in the availability of oxygen vacancies for hydration. A change in the local structure and, consequently, the appearance of different oxygen positions leads to a change in the size of oxygen vacancies (which are usually smaller than oxygen ions [57; 58]) and the inaccessibility of some vacancies for replacement by OH\({}^{-}\) groups. Therefore, an incomplete hydration occurs. Therefore, local distortions can cause different degrees of hydration for the samples with the same structural type.