2.4 HTS bulk materials Ë 35mini-magnet made of two YBCO samples.B 0 on top of a single sample was 12.5 T at
20 K and 9 T at 40 K.
A bulk YBCO superconductor as small as 2.4 cm in diameter covered with carbon
fiber fabric can trap an extremely high static field of 13.55 T at 34 K, and a bulk SmBCO
superconductor as small as 2.4 cm in diameter can trap an extremely high static field
of 13.69 T at 47 K [109]. Tomita and Murakami [110] prepared a YBCO bulk sample
with high flux trapping after improving the mechanical stability and the thermal
conductivity of the YBCO bulk. Their YBCO bulk was 2.65 cm diameter and trapped
a magnetic field of 17.24 T at 29 K. This is the highest trapped magnetic flux so far.
Using NdBCO/YBCO/MgO film seeds and the cold-seeding method in TSMG, Xu
et al. [111] successfully reprocessed failed bulks, and demonstrated a novel, conve-
nient, and effective process for recycling the failed REBCO bulks. Peng et al. [112]
reported that a large size SmBCO, 32 mm in diameter, was successfully grown in air by
the cold-seeding method. In the conventional TSIG process, three types of powders,
such as Gd 2 BaCuO 5 , GdBa 2 Cu 3 O 7 −x, and Ba 3 Cu 5 O 8 , must be prepared.
Yang et al. [113] has a new modified TSIG process technique, where only BaCuO 2
powders are required during the fabrication of the single-domain GdBCO bulk super-
conductors. Yang et al. [114] have observed in real time the growth process of single-
domain YBCO bulk superconductors using an in situ high-temperature video camera,
and obtained the growth rate of single domain YBCO bulk. The technique is helpful to
find solutions for modifying preparation processes of YBCO bulk as well as for improve
batch product quality.
Yang et al. [115] has reported a way to optimize the quality of the YBCO crystal
by TSMG fabrication, with NdBCO thin film seeds. The optimal growth conditions of
TSMG processing with NdBCO thin film seeds have been determined, and the optimal
growth method is helpful for engineering fabrication. Wu et al. [116] reported a new
approach for growing large single domains of YBCO by a TSMG process. Large YBCO
single domains of 53 mm in diameter have been successfully produced using this
method, and they predicted that samples with 75 mm in diameter can also be grown.
Shi et al. [117] have reported a successful multi-seeding technique for the fabrica-
tion of fully aligned, artificial (0°misalignment) grain boundaries within large-grain
YBCO bulk superconductors using bridge-shaped seeds. Plechacek et al. [118] have
developed a process capable of simultaneously fabricating up to 64 pieces of HTS
bulks. Zhou et al. [119, 120] have reported that the SIG of GdBCO single grains using
a YBCO-pressed pellet as the liquid source can successfully settle the liquid source
leakage problem, even atTmax∼ 1100 °C. The present method resulted in a significant
enhancement of the trapped flux density of the GdBCO grains.
In order to improve the processing of single domains with such large dimensions,
Noudem et al. [121, 122] proposed drilling artificial holes in the sintered powder before
the crystal growth. The single domain of YBCO bulk multiple holes can improve
mechanical properties, thermal stability, and the process of oxidation, and increase
interfacial flux pinning if the pores can be made sufficiently small. More efficient