Single-crystal growth and characterization of REBa2Cu4O8 and Y1−xCaxBa2Cu4O8

Abstract Crystals of REBa 2 Cu 4 O 8 (RE = Yb, Tm, Er, Ho, Dy, and Y 1− x Ca x ) were grown at 1100°C and 600 bar of O 2 pressure in a hot isostatic press furnace. Single crystal X-ray diffraction data show that all compounds crystallized in space group Ammm (#65) with the approximate lattice parameters a ≈ 3.82 A , b ≈ 3.86 A , c ≈ 27.1 A , and Z = 2 As the ionic radius of the lanthanide decreased, the lattice parameters decreased. Substitution of calcium in Y 1− x Ca x Ba 2 Cu 4 O 8 crystals ( x ∼ 0.02) increased T c to 87 K.