We studied the effect of oxygen partial pressure reduction to 0.05% during melt processing of NdBa2Cu3Oy, EuBa2Cu3Oy, GdBa2Cu3Oy, and (Nd,Eu,Gd)Ba2Cu3Oy on magnetic properties and microstructure. The superconducting transition of all the optimally oxygenated samples was as narrow as in those prepared in pO2 of 0.1%, the onset temperature of the present samples was slightly higher or at least same as for 0.1% pO2. Optical and scanning electron microscopy showed that in the GdBa2Cu3Oy and EuBa2Cu3Oy clusters are formed of sub-micron sized secondary phase particles. In other two compounds the secondary phase was uniformly dispersed. Magnetic properties of the present samples were always better at low fields than those of the samples prepared in 0.1% pO2. The irreversibility field data were rather controversial, in some samples improved, in others worse.
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