Influence of chemical composition on the stability of YBa$_2$Cu$_3$O$_y$ in a humid atmosphere

The influence of replacements of yttrium and barium in YBa$_2$Cu$_3$O$_y$ and doping of this compound with CeО$_2$, ZrО$_2$, and Pr$_2$О$_3$ on the capability of absorbing water from the annealing atmosphere at $T$ = 200$^\circ$C has been studied. The complication of the chemical composition of the 123-type compounds leads to an enhancement of their stability to aggressive components of the gaseous phase (H$_2$O, CO$_2$). These compounds have a variable chemical composition both in oxygen and water and can exist in three modifications: the oxygen-ordered ortho-phase, the oxygen-disordered tetra-phase, and the pseudocubic phase with a variable water content, which at $T$ = 200$^\circ$C separates into an oxygen-deficient water-enriched phase and an oxygen-rich anhydrous phase.