Growth and superconductivity of single crystals La$_{2-x}$Ba$_{x}$CuO$_{4}$

In 1986, Bednorz and Muller made a great discovery of the high temperature superconductivity in La$_{2-x}$Ba$_{x}$CuO$_{4}$ cuprate materials. Since the discovery of the superconductivity in high temperature superconducting oxide La$_{2-x}$Ba$_{x}$CuO$_{4 }$, a large number of groups have attempted to grow the single crystals. However, no single crystal La$_{2-x}$Ba$_{x}$CuO$_{4 }$with x$>$0.11 has been successfully grown. In this work, the effects of the growth condition and the compositions of a feed rod on the crystal growth of La$_{2-x}$Ba$_{x}$CuO$_{4 }$has been studied by an infrared image floating zone method. The experimental result shows that a planar solid-liquid growing interface tends to break down into a cellular interface when the growth velocity is more than 1 mm/h. When the planar solid-liquid growing interface break down into a cellular interface, the single crystal size decreases abruptly and the as-grown rod is not single phase. The large single crystals of La$_{2-x}$Ba$_{x}$CuO$_{4 }$with x=0 to 0.165 has been successfully grown. The single crystals of La$_{2-x}$Ba$_{x}$CuO$_{4 }$with x=0 to 0.165 up to 6 mm diameter and 150 mm length have been grown. The superconductivity transition temperature T$_{c}$ of as-grown single crystals of La$_{2-x}$Ba$_{x}$CuO$_{4 }$(x=0 to 0.165) have been measured.