A comparative study of superconducting LaBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7−δ</SUB> and La<SUB>3−x</SUB>Ba<SUB>3+x</SUB>Cu<SUB>6</SUB>O<SUB>14+δ</SUB>
- Ganapathi, L.
- Ganguli, A. K.
- Mohan Ram, R. A.
- Rao, C. N. R.
DOIAbstract
Based on X-ray diffraction and electron microscopy it is shown that oxides of the general formula LaBa2Cu3O7−δ become tetragonal when δ deviates slightly from 0. This tetragonal structure is similar to that of La3−xBa3+xCu6O14+δ, with a cubic perovskite subcell and triple periodicity. Electron micrographs of these tetragonal oxides show 90° microdomains. Orthorhombic LaBa2Cu3O7−δ with high Tc (~77 K) is found only when δ⋍0; this sample is subject to formation of twins. Fluorine substitution seems to favor superconductivity
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