44 Ë 2 Superconducting materials
Tab. 2.5:The mechanical properties for REBCO bulk materials.
Parameters Materials Units Values Ref.
Density (휌) YBCO-MTG g/cm^3 6.383 Theoretical max.
value
Vickers hardness (H) YBCO-TSMG (T) GPa 10.5±0.1 Roa et al. [136]
YBCO-TSMG (O) GPa 7.8±0.1 Roa et al. [136]
Elastic modulus (E) YBCO-TSMG pure GPa 177 ± 10 Foerster et al. [137]
YBCO-TSMG +10% Ag 2 O GPa 149 ± 4 Foerster et al. [137]
YBCO-TSMG (O) at 300 K GPa 193 ± 4 Roa et al. [136]
YBCO-TSMG (T) at 300 K GPa 192 ± 3 Roa et al. [136]
YBCO-TSMG (T)/(O) GPa 120 ± 5 Bartolomé [138]
GdBCO-MTG GPa 145 Fujimoto et al. [139]
DyBCO-TSMG GPa 120–160 Murakami et al.
[145]
Shear modulus (G) YBCO-MTG GPa 37–40 Krabbes et al. [63]
Fracture toughness
(KIC)
YBCO-TSMG pure MPa⋅m1/2 1.43±0.02 Foerster et al. [137]YBCO-TSMG +10% Ag 2 O MPa⋅m1/2 1.6±0.1 Foerster et al. [137]
GdBCO-MTG MPa⋅m1/2 2.2 Fujimoto et al. [139]
DyBCO-TSMG MPa⋅m1/2 0.8–1.6 Murakami et al.
[145]
Fracture strength(휎f) YBCO-MTG MPa 38–87 Koblischka-Veneva
et al. [140]
REBCO-TSMG MPa ∼ 70 Murakami et al.
[145]
GdBCO MPa 72 Fujimoto et al. [143]
Tensile strength (Rm) YBCO MPa 10–30 Sakai et al. [135]
YBCO MPa 18.4–77.4 Tomita [141]
Yield stress (휎ys) YBCO-TSMG GPa 3.58±0.10 Roa et al. [142]
YBCO-TSMG (T) and (O) are the tetragonal ofa-bplane and the orthorhombic phases along the
c-axis, respectively.
Murakami et al. [145, 146] reported the mechanical properties of the low-porosity
DyBCO bulks with different Dy211 contents and found that the bending strength and
the Young’s modulus of the low-porosity bulks were higher than those of porous Dy123
bulks.
The evaluation on the mechanical properties of an REBCO large single grain bulk
of diameter 150 mm at liquid nitrogen temperature (77 K) was carried out by Murakami
et al. [147] in 2013. Fracture strength data at 77 K were obtained through bending
tests for planar specimens. The average fracture strength (휎fave) was about 70 MPa.
The휎faveof the large single-grain bulk at 77 K was slightly higher than that at room
temperature.
Another important problem in the engineering applications of HTS bulks is
the rapid and irreversible degradation due to exposure to ambient atmospheric