For synthesizing a high-quality YBa2Cu3O7-x superconductor using a domestic
microwave oven without any post-heat treatment, the power;and time of micr
owave 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 i
n the proper way. The conditions of the sample inside the oven are almost t
he same as the sample environment proposed by Rare et at [Jpn. J. Appl. Phy
s. 36 (1997) L1291]. The maximum monitoring temperature where crystal growt
h occurs rapidly for a high-quality YBa2Cu3O7-x superconductor is shown to
be about 500 degrees C which is much lower than the maximum heating tempera
ture. in the conventional method.