Synthesis of YBa2Cu4O8 Powders by Sol-Gel Method under Ambient Pressure

Abstract
The 124 superconductor YBa2Cu4O8 was synthesized using a sol-gel method with starting solutions contained stoichiometric compositions of Y/Ba/Cu=1/2/3 and 1/2/4. Heattreatment was done below 800°C in 1 atm oxygen atmosphere; neither special equipment nor additives were required. Our result suggests that the 123 phase is thermodynamically metastable in the temperature region that had been thought to be the equilibrium region of 123-orthorhombic phase.