Levitation of NEG-123 at the temperature of liquid oxygen (90.2 K)

A long-term Zr₂O₃ ball milling of Gd₂BaCuO₅ secondary phase particles dispersed in the melt-textured (Nd_0.33Eu_0.33Gd_0.33) Ba₂Cu₃O_y (NEG-123) compound brought a superb enhancement of electromagnetic performance of this composite at high temperatures: at 77.3 K, J_c reached 192 kA cm^-2, at 90.2 K (temperature of liquid oxygen) the remnant J_c was 40 kA cm^-2, a value high enough for levitation experiments. Energy dispersive x-ray analysis found small Zr-rich secondary phase particles of only 20-50 nm in size, while the mean particle size after the milling was 70-200 nm, according to the milling time. This new particle size reduction mechanism enables the design of non-contact liquid oxygen pumps for industrial applications.