Fabrication of Ca-doped REBa2Cu4O8 films by the molten hydroxide method

Fabrication of a superconducting YBa2Cu4O8 film via coprecipitation

“…On the other hand, REBa 2 Cu 4 O 8 (RE-124) has a rigorous thermal stability for oxygen contents at high temperature up to 800 • C. [14][15][16][17] In addition, the superconducting transition temperature (T c ) of RE-124 can be increased up to 90 K by a partial Ca substitution of RE site. 18,19) Hence RE-124 is an important material for superconducting application above liquid nitrogen temperature that does not contain toxic elements as well as RE-123 and Bi-2223. Up to now, synthesizing RE-124 superconductor to good quality for application has been considered to be difficult.…”

“…[15][16][17][18][19] In particular, Y-124 exhibits a higher superconducting transition temperature T c (∼80 K [15][16][17][18][19] ) than the liquid nitrogen temperature and its T c can be increased up to 90 K by the partial Ca substitution of the Y site. 20,21) Hence Y-124 is an important material for superconducting application above liquid nitrogen temperature. However, it is not easy to synthesize the Y-124 phase under ambient conditions according to the pressure-temperature phase diagram of the Y-Ba-Cu-O system.…”

Increasing theTcof YBa2Cu4O8to 90 K by Sr substitution via the KOH flux method

“…11,20) Single crystals of Y124 and of Y124 with other rare-earth elements substituting for Y (RE124), have also been grown from molten hydroxide solutions at low temperatures ranging from 475 °C to 800 °C. [21][22][23][24][25][26][27][28][29] Y124 and RE124 crystals grown from molten KOH solutions show a sharp superconducting transition despite the low growth temperature of approximately 700 °C. [22][23][24] These crystals even exhibit a higher T c than those prepared using other synthesis methods, 25,26) indicating higher crystalline perfection.…”

Single Crystal Growth of Cuprate Superconductor (Lu0.8Nd0.2)Ba2Cu4O8 by KOH Flux Method

“…It is well known that the Y site in YBa2Cu3O7- (Y123) can be completely replaced by some of rare-earth (RE) elements and almost all RE123s show superconductivity at ~90 K. 1,2) Similarly, the Y site in YBa2Cu4O8 (Y124) can also be replaced by several RE elements but the superconducting transition temperature (Tc) of RE124 varies between 70 K and 80 K. [3][4][5][6][7] Up to now, a series of RE124 has been obtained for RE = Sm, Eu, Gd, Dy, Ho, Er, Tm and Yb, and the Tc of RE124 increases from 70 K to 80 K dependent on the decrease of the c-axis in this order. [3][4][5][6][7][8][9][10][11] In that sense, Lu124, consisting of the smallest RE ion of Lu, is expected to show the highest Tc in the RE124 system since it has the smallest c-axis length.…”

“…Single crystals of RE124 for RE = Sm, Eu, Gd, Dy, Ho, Er, Tm and Yb were grown under ambient pressure by the potassium hydroxide (KOH) flux method. [8][9][10][11] However, Lu124 has not been synthesized yet due to the large lattice mismatch of the perovskite units caused by the small size of Lu 3+ ion, similar to the situation of Lu123. 12) If the lattice mismatch is reduced by partial substitution of Lu with a larger RE, the Lu124 structure can be stabilized.…”