We have investigated the ternary compound superconductors (Nd0.33Eu0.33Gd0.33)Ba2Cu 3Oy (NEG), (Sm0.33Eu0.33Gd0.33)Ba2Cu 3Oy (SEG) and (Nd0.33Sm0.33Gd0.33)Ba2Cu 3Oy (NSG) melt-processed in a reduced oxygen atmosphere with magnetic and magneto-optical measurements. Zero-field-cooled and field-cooled measurements were carried out in order to correlate the flux distributions with microstructure analysis. It was found that the critical state is well established in all three samples. The Jc(B) curves derived from magnetization loops exhibit a strongly developed secondary peak effect. Scaling of normalized Jc as a function of reduced field, b = B/Bpk, was performed. At 77 K and above, it was found that NSG and SEG samples have similar properties, which are different from those of the NEG sample. The current-carrying length scale was determined from the reverse leg of the magnetization hysteresis loops and was compared with the actual dimensions of the sample.
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