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

A long-term Zr 2 O 3 ball milling of Gd 2 BaCuO 5 secondary phase particles dispersed in the melt-textured (Nd 0.33 Eu 0.33 Gd 0.33 )Ba 2 Cu 3 O 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.