{'fraction_non_alphanumeric': 0.03788334335538184, 'fraction_numerical': 0.02465423932651834, 'mean_word_length': 5.028985507246377, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Synthesis and characterization of YBa2Cu3-xSbxO7-δ high-temperature superconductors

The effects of Sb doping on YBa2Cu3O7-δ high-temperature superconductors have been investigated. Samples were synthesized for the nominal compositions of YBa2Cu3-xSbxO7-δ where x = 0.0-0.3 by solid-state preparative techniques. These materials were prepared under different conditions, such as heating in an air or an oxygen flow, followed by furnace cooling or quenching in air or in liquid nitrogen. These results show that for the air-quenched samples these materials are superconducting when 0.01⩽x⩽0.1, whereas for the furnace-cooled samples Tc gradually decreases with increasing Sb concentration. However, in both cases zero resistance was not achieved down to 72 K when x⩾0.2. To understand the effects of Sb doping on the structure of YBa2Cu3O7-δ x-ray absorption spectroscopy, x-ray diffraction and scanning electron microscopy have been applied. These results indicate that the valence state of copper is almost the same in the pure and the doped YBa2Cu3-xSbxO7-δ. It has been observed that doping with low concentrations of Sb (x⩽0.1) and slow cooling have similar effects on the structure of YBa2Cu3O7-δ, i.e. these help to stabilize the orthorhombic structure. Whereas, with higher concentrations of Sb (x⩾0.2), all compositions of liquid-nitrogen-quenched YBa2Cu3-xSbxO7-δ and air-quenched pure YBa2Cu3O7-δ stabilize in the tetragonal geometry. In superconducting materials the particles are smaller, uniformly distributed and the grains are linked together, whereas in non-superconducting materials the particles are larger and the grains are not well connected.