Orthorhombic-tetragonal phase transition inLaBa2Cu3O7−ywith zero resistance at 92 K

The orthorhombic-tetragonal phase transition in $\mathrm{La}{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-y}$ is studied under a ${\mathrm{O}}_2$ gas atmosphere by thermogravimetry, differential thermal analysis, and differential scanning calorimetry. Our sample has good homogeneity and shows a sharp superconducting transition above 90 K. The determined transition temperature is 481 °C at which the oxygen deficiency, $y$, is 0.13. The results are discussed together with the previously reported data concerning $L{\mathrm{Ba}}_2{\mathrm{Cu}}_3{\mathrm{O}}_{7-y}$ ($L$: rare-earth element).