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The growth process of single domain YBCO bulk superconductor by top-seeded infiltration and growth technique has been observed in real time by an in situ high temperature video camera. The initial epitaxial growth temperature from the NdBCO seed and growth rate of a single domain YBCO bulk were obtained by measuring the growth distance between the seed and the growing interface at different times. It was found that the initial epitaxial growth temperature of YBCO crystal is about 1008 °C; the average growth rate (R a) is increasing with time at first, reaches a highest value about 0.28 mm/h in the range of under cooling temperature(ΔT) 18–20 °C, and decreases to 0.26 mm/h until the single domain YBCO bulk grown up to the whole sample at about ΔT = 22 °C. In addition, It is also discovered that the instantaneous growth rate(Ri) is a random scattering data with time and ΔT, R i varies from 0.04 to 1.14 mm/h and without any order. These results were observed for the first time.

Effects of additional permanent magnet on the levitation force of a single domain GdBCO bulk superconductor have been investigated with a cylindrical permanent magnet in their coaxial configuration under zero field cooled state at liquid nitrogen temperature. The magnetic polarity N of cylindrical permanent magnet is pointed to the GdBCO bulk superconductor, and the two additional permanent magnet of rectangular parallelepiped shape are fixed on two sides of the GdBCO bulk superconductor in different arrangments. It was found that the levitation force can be improved to about 61.5 N, which is more than 2 times higher than that (29.8 N) of the system without the additional permanent magnet, when the magnetic polarity N of two additional permanent magnets points to the GdBCO bulk superconductor in horizontal direction. The levitation force is reduced to 19.6N, which is about 65.8% of the levitation force 29.8N of the system without the additional permanent magnets, when the magnetic polarity N of two additional permanent magnet are antiparallel to the magnetic polarity N of the cylindrical permanent magnet. The results indicate that the levitation force of high temperature bulk superconductors can be effectively improved by introducing additional permanent magnet based on reasonably designing the system configuration, which is very important during the practical design and applications of superconducting magnetic levitation systems.

Compared to the conventional melt growth (MG) method, the top seeded infiltration and growth (TSIG) process is an effective way for preparing bulk REBa2Cu3O7−x (RE-123) with finely dispersed RE2BaCuO5 (RE-211) particles. However, it is more complicated and time-consuming, because three kinds of precursor powders, namely, RE-211, RE-123 and BaCuO2, have to be prepared for the conventional TSIG process. In this paper, a new liquid source (NLS) composed of RE-211 and Ba3Cu5O8, was proposed for simplifying the TSIG process, which is different from the regular liquid source (RLS) composed of RE-123 and Ba3Cu5O8. In this modified TSIG technique, we need to prepare only RE-211 and BaCuO2 powders. Single-grain GdBa2Cu3O7−x (GdBCO) bulk superconductors have been fabricated using the RLS and NLS separately. The morphology, microstructure and levitation force of the bulk GdBCO have also been investigated. The results indicate that the NLS can be used to simplify the process flow and improve the efficiency on the fabrication of single-grain GdBCO superconductors.