Growth and characterization of a new superconductor GaBa2Ca3Cu4O11+δ



 By using the Walker-type high-pressure synthesis apparatus, we have successfully grown a new superconductor GaBa2Ca3Cu4O11+δ
 (Ga-1234) with a transition temperature of 113 K. X-ray diffraction (XRD) measurements on the powderized samples show a mixture of the Ga-1234 phase and the Ca0.85CuO2 phase, but the former is dominant. Under the scanning electron microscope (SEM), plate-like crystals of the Ga-based 1234 phase with shiny surfaces can be seen. And the obtained local chemical compositions revealed by energy dispersion x-ray spectroscopy (EDS) are very close to the stoichiometric values. On some sub-millimeter crystal-like samples of the 1234 phase, we obtain a full Meissner shielding volume. From the temperature-dependent magnetizations, we determine the irreversibility fields and find that the system exhibits a highly anisotropic behavior.