Controlled Microwave Irradiation for the Synthesis of YBa 2 Cu 3 O 7-x Superconductors

For synthesizing a high-quality YBa 2 Cu 3 O 7- x superconductor using a domestic microwave oven without any post-heat treatment, the power and time of microwave irradiation are controlled by monitoring continuously the temperature of the microwave-heated sample. The temperature is measured by means of a metal-sheathed chromel-alumel thermocouple which is installed in the oven in the proper way. The conditions of the sample inside the oven are almost the same as the sample environment proposed by Kato et al. [Jpn. J. Appl. Phys. 36 (1997) L1291]. The maximum monitoring temperature where crystal growth occurs rapidly for a high-quality YBa 2 Cu 3 O 7- x superconductor is shown to be about 500°C which is much lower than the maximum heating temperature in the conventional method.