  This work examines the oxygenation process of polycrystalline powder of
YBa$_2$Cu$_3$O$_{6+\delta}$ superconductor material through constant
temperature thermogravimetric analysis. Starting from completely deoxygenated
samples ($\delta$ = 0), both the mass evolution in an oxygen atmosphere and a
differential temperature value referenced to an inert sample (alumina powder)
subjected to the same experimental conditions are recorded. The oxygenation
process itself is identified as an exothermic process accompanied by a second
also exothermic associated process. This second process is identified as the
Tetragonal-Orthorhombic transition present in the material. Based on the
obtained results, the structural phase diagram of the material is
reconstructed. Issues of metastability of the structural phases, as well as the
potential of the equipment used to obtain these results comparable to those
obtained in large facilities, are discussed. Reinterpretations of previously
discussed works in the literature are inferred.
