Growth and superconducting properties of (Eu,R)Ba₂Cu₃O_7−δ(R = Er, Tm) single-crystalline whiskers

Abstract

We have grown single-crystalline whiskers of superconducting (Eu, R)-123 (R = Er, Tm), systematically changing the ionic radius by means of doping with Er or Tm, which have smaller ionic radii, in place of Eu. We tried to gain an understanding of the oxidation, doping and superconducting state of the materials by annealing whiskers at different conditions, studying the temperature dependence of the magnetization and carrying out x-ray diffraction analysis and quantitative electron probe microanalysis measurements. We observed that Eu-rich whiskers, which require higher temperature for growth, are more liable to have oxygen deficiencies and structural instabilities. Upon Er or Tm doping both the oxygen deficiency and the substitution of rare-earth elements at the Ba site decrease. Our results show that the carrier doping can be systematically controlled, from the highly underdoped to the slightly overdoped range, by making a suitable choice of the ionic radius of the rare-earth elements in the as-grown whiskers.

Growth and Anisotropic Properties of RBa2Cu3Ox Single-Crystal Whiskers

“…The cause of the lower T c of the Gd-123 whiskers is the substitution of Gd 3+ ions for the Ba 2+ sites in Gd-123 whiskers and the oxygen deficiency in Gd-123 as-grown whiskers. It was reported that the T c of Ca-containing R-123 as-grown whiskers was markedly increased to about 80 K by annealing in oxygen 6,14) . Therefore, the lower T c of the Gd-123 as-grown whiskers is mainly due to the oxygen deficiency in Gd-123.…”

“…It was reported that the T c of Ca-containing R-123 as-grown whiskers was markedly increased to about 80 K by annealing in oxygen. 6,14) Therefore, the lower T c of the Gd-123 as-grown whiskers is mainly due to the oxygen Table I. Lengths of whiskers grown under optimum growth conditions, such as nominal compositions of precursors, heat treatment temperature (T max ), holding time at T max (t max ), and rate of cooling to 900 C (C R ).…”

Growth of whisker-like and bulk single crystals of PrFeAs(O,F) under high pressure

“…In the case of the high temperature superconducting single crystal whiskers, the Bi-Sr-Ca-Cu-O system is most popular, probably due to relatively easy fabrication [17,[24][25][26][27]. The whiskers were also observed in RBa 2 Cu 3 O 7+x systems with R = rare earth elements [17,28,29], whereas little is known about whisker growth and their properties in the Tl-and Hg-based superconductors [30]. For the case of Bi2212 and Bi2223 cuprate superconductors various mechanisms were proposed, as summarized in review by Badica et al [27].…”

Effects of SnO on growth and physical properties of BSCCO whiskers

“…[3][4][5] Many attempts have been done to fabricate single crystal superconducting whiskers using different superconducting systems and techniques. Pure and Al, Ag, Er, Pb, La, Te, Ga, Ge, K, Na, Co, Fe, Zn and Li doped Bi-2212, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] pure yttrium barium copper oxide (YBCO), [21][22][23] a series of RBa 2 Cu 3 O x (R5Sm, Eu, La, Nd, Tm, Yb, Lu, Ho, Dy and Gd), 24,25 Ca and Te doped EuBa 2 Cu 3 O x 26 and MgB 2 27 are only some of the examples for such studies.…”