Interaction of binary cuprates with oxygen and water vapor at temperatures of 200–400$^\circ$C

Interaction of binary cuprates with oxygen and water vapor at $T$ = 200–400$^\circ$C has been studied. It has been established that only compounds containing oxygen vacancy chains in their structure can absorb oxygen and moisture from annealing atmosphere. Absorption of oxygen brings about decrease in the lattice parameters while embedding of OH$^-$ groups leads to their growth. In contrast to YBa$_2$Cu$_3$O$_y$, binary cuprates do not undergo phase transitions in interaction with the atmosphere. Saturation with water and formation of oxyhydroxides is followed by their hydrolytic decomposition involving formation of simpler oxides and hydroxides.