Structure and superconductivity in Y1−xCaxBa2Cu3O7

Characterization and synthesis of Y0.9Ca0.1Ba1.8Sr0.2Cu3O7−δ via combining sol–gel and solid-state route

“…The lattice distortion is contributed by the difference of ionic radii between the doping element with the native element. Many reports [4][5][6][7][8][9][10] show that with fixed oxygen stoichiometry, the substitution of Ca for Y generates holes at CuO 2 planes which has influence over superconducting transition temperature without changing the crystal structure of the sample due to slightly difference between the ionic radii. However, it was found that oxygen vacancies (which fill holes) are always cointroduced with Ca, thus reducing its holes generation effect [4].…”

“…Ca 2+ valence is smaller than the one of the substituted Y 3+ that can result in increasing number of hole [6][7][8][9][10][11]. Anyway, increasing Ca content to replace Y in Y-123 phase was found to be accompanied by decreasing oxygen content [4][5][6][7][8][9][10][11]. According to Awana et al [11] on replacement of Y by Ca, the oxygen content of Y 1Àx Ca x Ba 2 Cu 3 O 7Ày (y % 0.3) system remains nearly unchanged, till x = 0.1 and drops sharply to x = 0.15, which is followed by decreasing bond distances Cu-O planes with increasing Cu(2)-O(2)-Cu(2) angle.…”

“…Many researchers [5][6][7][8][9] have long attempted the substitution of Ca for Y in Y-123. Ca-doped YBCO is particularly of interest in the study of the electronic properties of CuO 2 planes and the C-O chains.…”

YBCO bulks for preparation of permanent magnets

“…In the case of YBa 2 Cu 3 O 7 compound it was shown, that the calcium solubility in Y123 is limited and the crystal structure of Y 1−x Ca x Ba 2 Cu 3 O y remains orthorhombic for x < 0.3. 12 By addition of Pt dopant 9,13 advantageously can be influenced the uniform distribution of small particles of Y211 phase within Y123 domains. They act as flux pinning centers, 14 promising higher trapped fields.…”

Mechanism of a strong rise of T due to the calcium doping in Y1−Ca Ba2Cu2.8Zn0.2O

“…[8] and references therein). Due to its lower valence relative to the valence of substituted yttrium, calcium doping leads to an increasing oxygen deficit [7][8][9][10][11][12], thus compensating the influence of the first impurity on the charge balance in the lattice. For this reason, the oxygen content in the Y 1Àx Ca x Ba 2Àz La z Cu 3 O y and Y 1Àx Ca x Ba 2 Cu 3Àz Co z O y systems with fixed z goes down with x towards its stoichiometric value y % 7 that induces the oxygen subsystem ordering and, as a result, an increase in the T c value [7,8].…”