CHARACTERIZATION OF THE HIGH-Tc PHASE AND ITS METAMORPHIC PHASES, Ba2YCu3O7 - delta .

Sintered samples of good quality of the four different phases, Ba//2YCu//3O//7// minus // delta , were reinvestigated by means of resistivity, susceptibility and specific heat experiments. The specific heat of the 90 K superconducting phase revealed a distinct jump at T//c of DELTA C//p/T//c equals 53 mJ/molK**2 and in the superconducting state a small but finite value of gamma of about 8 mJ/molK**2 was discerned at low temperatures. Variation of these parameters in its metamorphic phases with different oxygen content is discussed in relation to other physical properties and sample quality.